You bring up an interesting question actually. What is a "perfectly valid in-character role-playing" choice? That's going to vary really, really wildly depending on the group and playstyle. Obviously, for some, buying 10000 gp necklaces is something they think is reasonable for a PC adventurer. For others, that's pretty ridiculous, bordering on straw-man since it's just not going to happen in their group.
The designers have to choose one or the other. Otherwise, you start crossing the streams and get into all sorts of trouble balance-wise. If one of the group uses mundane items for cool, another does it to totally min-max his character, a third does it for both and a fourth completely ignores it entirely, you get an unholy mess of power levels within a single group.
What I'm getting at is that it shouldn't make that much of a difference, but it does in newer editions because the math has become so fine-tuned. And that's a bug.
If I've got 10K g.p. to burn and I spend it on a manor house, where my fellow party member spends her 10K on a fancy sword, then OK maybe she's going to hit a bit more often than I do and hurt things a bit more when she does, but so what? The system ought to be able to handle that. But I've a germ of a theory why it doesn't so well any more.
There are too many levels.
In something like 0-1-2e, where you realistically only had about a 10-level range in the game both for PCs and monsters, the math was non-granular enough to be quite forgiving around the edges. A fully-twinked party could go into the same module as an under-optimized bunch of clods, and both could have fun and have a chance at survival.
But in 3e with a 1-20 spread and open-ended monsters, and 4e with a 1-30 spread, the game's math is forcing the characters to function within a narrower and narrower "window" of power level relative to what they're facing; and because of that every extra bonus makes more of a difference. Couple that with the idea of mundane items giving bonuses (I don't agree with this; I'd go the other way and suggest lack of suitable mundane items for the job gives penalties) and the fluff-laden donkeyhorse turns into a mechanical headache.
Like I said before, we saw precisely this in 3e. Fifteen bajillion character options spawn the Char-ops board that comb the supplements in order to create precisely this problem.
And here I think we agree. Char-ops boards are the definition of Gaming Evil, as far as I'm concerned; and while I realize some people enjoy that sort of thing that same sort of people are the sort of people who'll be playing at tables other than mine.
In all of this I'm not in the least suggesting that mundane items should give bonuses. Lack of them should give penalties (you'll be at -5 if you're only using your bare hands to open that chest); and either way their existence needs to be tracked. And, if you're bringing a toolkit into the dungeon, you'll probably need a donkeyhorse to carry it, thus we're right back where we started: where's my freakin' mule!
And yes, some will say that's too much bookkeeping; but really: how much effort is it to once every dozen sessions or so write a quick list on your character sheet of the mundane gear you're carrying?
Which spins it all right back around to, what do you consider to be a perfectly valid in game decision for a PC to make?
Pretty much anything that makes sense for the character, in character.
One other variable that just occurred to me that probably weighs quite heavily on this discussion in terms of 4e: as a system it seems to be very frugal with treasure compared to what has gone before. And if you're short of cash, you're probably going to want to spend what you have on adventuring necessities first. In older editions, in my experience it's quite possible to have cash left over once you've loaded up with magical field gear, and thus spending it on castles and jewelry wasn't such a big deal. That, and it was much harder to go and buy/build what you wanted.
Lan-"I hope this makes more sense to you than it does to me"-efan
