I see this sort of criticism a lot, and it strikes me as a bit too flip. Obviously there is the potential for PCs to cause local inflation if they pull a lot of money out of a dungeon and then dump it all in a small town. But a few thousand gold pieces, even a few tens of thousands, won't upend the economy of a medieval kingdom. It's quite possible for D&D to provide consistent and sensible prices for items assuming adventurers are rare and their treasure hauls limited. Then you can toss in some guidelines for DMs to deal with how things might change if they depart from that model.
But those assumptions aren't true for Forgotten Realms. Or Greyhawk. Or for most other major current settings, with Eberron standing out as the major WotC exception of which I'm aware.
And even allowing that those assumptions are true for a given setting, I'm still going to argue that the discovery of several tens of thousands of gold pieces still has the potential to create devastating levels of monetary inflation, depending on the details of the economy into which the gold is dropped.
In the end, I think that's the problem: a well-thought out macroeconomy will be pretty setting-specific. I don't think that inflationary concerns prevent a person from thinking out the economy of a given setting, but they do prevent a person from writing out a single, coherent price list that encompasses even a majority of the ways that the game actually gets played.
OTOH, I can see a good, detailed essay going over the creation of a D&D economy and detailing the important decision points in the creation process. Not confident about the market for this product, though.
I disagree. I give you ACKS, the game I bought only because it got the a meaningful and consistent in-game economy.
ACKS is different than your typical D&D game in that ACKS players are expected to spend their loot on private and public sector investment. Games like this do happen, but I don't think it's reasonable these days to consider this stuff typical for D&D. (I say this despite being a huge Birthright fan.)
Not strictly true - history tells us what happens to an economy when there's a gold rush on.
There are lots of historical examples of commodity currency inflation. (The spanish empire makes a great case study, IMO.) I'm suggesting that these scenarios would be pretty restrictive to place upon D&D in general--although they certainly run closer to what I would expect to see in a world that responded realistically the PCs actions.