See, by responding to an insight by telling me that the mechanic wants to make "a lot" of money, you are setting me up to believe he is lying to get more money.
But beyond that, you are telling me his goals, and if I rolled to find out a merchant wants to make money, I'd probably ask the DM if they want me to roll for realizing water is wet while I'm at it.
But what is their intent? Are they intent on gouging me for as much as I'm worth? Are they intent on providing the best service they can?
Because that is what the player is likely asking anyways, is that price a real price or an inflated price.
And frankly, why do this to someone anyways?
I've had cars that needed to go to mechanics constantly, and I hate dealing with that sort of "toss a coin, you don't know" BS. Are you really advocating putting players through that just for the sake of realism? Is the best they are going to get from insight things like "The farmer doesn't want to die" "The merchant wants to make money" "The King thinks you should listen to him"
The skill says it lets you figure out intentions. Is the mechanic intending to gouge me with false problems or inflated prices is a legit question, and your non-answer of "he wants to make a lot of money" means that we wasted our time, because I didn't need a skill roll to know that.
I may have phrased it poorly, but I think there's a difference between a merchant/mechanic "wanting to make money" (which is obvious) and the player/customer realizing that this particular merchant/mechanic is being greedy.
So let me elaborate a little bit.
First, if this is just a normal transaction, and the NPC is just a shop owner with no other role to play in the adventure, then I'm going to signal that to the players so they don't waste time. (And by "signal" I might mean something along the lines of, "He's just shop owner...he doesn't know anything.")
Now, I realize some people don't like that. They want the platonic ideal of a sandbox, where every NPC is a roleplaying opportunity that may lead to adventure. I don't like to play in games like that, and I don't run games like that. Table time is too scarce, and from my experience it's usually one player who wants to engage in a deep conversation with every NPC while everybody else sits around and fiddles with D&D Beyond. Also, I have very little interest in tracking copper pieces and haggling over prices. Unless something is going to cost a significant chunk of a character's stash I tend to hand-wave prices: I don't make players account for every mug of ale and night in an inn. So making skill checks (sorry, iserith, I meant ability checks with skill proficiency modifiers) to haggle over prices just doesn't interest me.
Ok, so with that out of the way, let's assume we're talking with an NPC who plays a more active role in the story. Somebody who, depending on how the interaction with the players go, could affect the outcome. And that's the core of it for me:
will this interaction affect the trajectory of the story in a meaningful way? If so, then the merchant's...let's say he's a merchant...the merchant's "true intentions" matter. The players might, during negotiations (which itself, in my game, is a signal that this NPC is relevant) over a price for something, glean that he:
- Wants to gouge them
- Wants to be highly respected for his products/services
- Enjoys haggling for its own sake
- Is trying to rush them out the door
- Is trying to keep them here
- Doesn't want to do the work but won't say so
- Is fishing for something other than money
- Is lonely and just wants to talk
I lost momentum but with a little thought I could keep going. Do you see how each of those "true intentions" could be a hint as to the 'truth' of what he is saying, without it being a true/false lie detector? And maybe how using that clue as a basis to decide what to do next is a lot more fun than just rolling an 18, being told he's lying, and acting accordingly?
What clues did you seed into the world for Horse Trader #54 overcharging them for a riding horses?What series of events led to the clues the players will use when they randomly decide to search a traveling merchant's wagon that you only had pass by to deliver news of an orc presence to the south?
Clues and breadcrumbs work great for major plot points. For minor stuff that your player's blindside you with, not so much.
Hopefully what I wrote above addresses those questions/points.
My players recently broke into an enemy castle to free it from the influence of a cult of Orcus. The criminal asked to search for valuables and loot the place. It makes perfect sense, it also makes sense there are hidden treasures in the royal chambers. Didn't plan on it though, because mostly the paladin and cleric keep him reined in and not stealing everything (players are fine with the dynamic, and they all loved him turning it on them).
So, should I not have allowed him to search for treasures in the royal chambers?
No, that seems a ridiculous answer. But, I also wasn't going to spend 10 minutes coming up with answers and deciding DC's only to have him roll a 1 (or a 2 or a 3, I know auto-fails are a houserule). So he rolled, and I decided based on his roll. It saved time and let him do something in character that made total sense.
As I mentioned in a previous post, this is the perfect place to use straight up dice rolls. I might do something like, "Ok, it's going to take a few successes with a high DC, and every attempt takes a few minutes, during which I am going to roll to see if the guards stumble upon you. What do you want to do?" It's not just make a roll, and if you succeed you find treasure, if you fail you don't. There's no consequences to that, no trade-off. (And I think the core idea underlying all meaningful games, not just RPGs, is
trade-offs.)
In fact, just in general I would say that if there's no downside to failing a roll, I would rather not have a roll. In combat, missing your sword swing is bad. At the very least there's an opportunity cost: you would have been better off taking the Dodge action. Or spending Inspiration. Or whatever.
In fact, in the merchant example above I struggle with having any die roll at all, for exactly that reason. I might simply give a clue to whoever has the highest Insight. Or spread them around, if there are several clues. Just because there's no cost to failure of an Insight check. (And consequences can help mitigate "Can I roll, too?" syndrome.)
(This is why I kind of like the idea of a "lie detector" sub-system/mini-game, using a combination of Insight, Investigation, Persuasion, and Deception, which is an intentional attempt to trap somebody in a lie. It can be done purely mechanically, with dice, preferably over several rounds of rolling, and can give you a binary answer*, but it comes with a trade-off: you can easily anger the NPC.
*binary in the sense that you can determine he is lying, or be unable to determine he is lying, but maybe can't 'prove' he is telling the truth.)
And I'll also add, a lot of my players don't have the mental space to remember all my clues. I'm lucky this semester to have a player willing to take notes we can refer back to, but we play in a weekly game and expecting someone to remember a clue that might have been given over 160 hours ago when they had an entire week full of other things to deal with.... Yeah, I'm only doing that for the big things in the main plot, it wouldn't make sense to try it any where else.
Yes, that's an issue. I also have a couple of players who take notes, and I also email around a synopsis before each session.