Actually, I WOULD use the skilled hireling rule, which means it WOULD cost more. A company of mercenaries would include corporals to manage squads, sergeants to manage the corporals, a lieutenant and a captain. The skilled hireling rules specify very clearly that the 2gp price is the MINIMUM, so those others would be more and the officers considerably more. Base mercenaries don't just hang around to be hired. They are groups.
Okay. Triple the price then. Instead of 100 per day it is 300 per day.
The troll hoard still pays for 6 days of that mercenary company. Again, there was no issue with the amount of money in the troll hoard, but the amount could still be used for the same shenangins that would break the game with wealth that people bring up.
Yes. A riskless roll to just get money for sitting around is more free than going into the very, VERY highly risky underdark and happening across a mindflayer body. Not only could there be other mindflayers around, but whatever manage to kill it is probably also in the area. Have fun with that. Actually, it would be fun, but hardly free.
So, it isn't the amount of money. It is about the risk. Which, again, was touching upon my exact point. There seem to be people who think it is a problem to earn larger sum of money without taking that risk. Without going into a place like the Underdark (which I never claimed that you did go into the Underdark, and actually, you are assuming that whatever killed the mind flayer is hostile to the players, and not that the players killed it.)
But, again, why? Would it be more acceptable to have my smithy on the edge of a fetid swamp where I could be attacked any day by monsters and then I could make more money than is currently allowed by the system? Why is it that we need money to be balanced by risk? It isn't like we assume that any given merchant prince took great personal risks to their body to make their fortune. Many noble families aren't full of adventurers. And if they can get wealthy without taking personal risk of bodily harm... why can't the players?
Is it because there is a fear that if the players do this... that they won't want to adventure and play Dungeons and Dragons? Why? Isn't their motivation to play more than their fake characters making fake money?
It's good for Luke and Leia that he 1) hated the empire with a passion, and 2) had a crush on Leia that turned into love.
In other words "motivations other than money" which is literally what I said. Right here, with this sentence:
There is no need to fear "free" money, as long as your players have a motivation beyond profit.
Fun how I seem to.. know my own point
The carpet is faster, can be carried with a group(though still bulky), doesn't require a hired crew and is more maneuverable. That makes it much better for an adventuring group.
The carpet also has a specific price, which you the DM give it. The DMG gives 5000-50000gp as the range for rare items, not for flying carpets. Where in that range it specifically falls is part of 5e's mantra of rulings over rules and is for the DM to decide. He should have a good idea based on other rare items. Weaker rare items fall towards the 5k end of the range. Stronger, better items fall towards the 50k end of the range. Middle strength items? You guessed it. Around the 25k area of the range. It's not rocket science.
You also need to get a galley with better gas mileage.
And you miss the most basic point.
Yes, the carpet can be carried by the group. Yes the carpet is more maneuverable. This increases some of its utility... but the DMG had zero issue giving an exact number for a flying ship, run by a crew, carrying a load. Which could be insanely helpful for a group. Having an airship can be game defining. And that was given a solid price. 20,000 gp. Even with all the factors that might change how useful that is, and all the GM rulings that might go into it.
But the carpet... gets a range and they leave it up to the DM to decide the price. Why? The game designers had no problem giving us a specific price for the highly situational purchase of a flying ship, but they just couldn't possibly make the same decision for a flying carpet? Because they might unbalance something? That is nonsensical.