You don't have to have access to Wish at low levels, but if you don't, and you don't come up with some way to handle magical items and wealth, then 3E is forever going to be tied to that model. Because wealth = power, then suddenly you can't do stuff like give dragons treasure hoards big enough to sleep on.
You can, you just need to make sure the dragons with enough power to acumulate a bed of gold are major enemies that will cost the party an arm and a leg to defeat (after going over their minions, trapped dungeons and stuff) and happen like once or twice a campaign. Because dragons with beds of gold shouldn't be reduced to a road ecounter.
Seriously, a dragon's hoard of gold coins could fit in your backpack. That sucks.
If dragons are common easy ecounters around every corner, I would say that sucks even more. This is, if money is completely worthless, why's the dragon acumulating it? Is it some dumb lizard that only cares about shiny baubles? Where's the glory on killing that?
A real dragon would make his bed out of raw chaos or crystalized souls or whatever passes by viable currency in your seting. Dragons reduced to sleeping over shiny trash aren't worth the time to put them out of their miseries on my opinion.
The game shouldn't fall apart if the PCs come across an entire cave full of coins.
It doesn't.
-The cave full of coins is as well filled with monsters waiting in ambush.
-The money is cursed (see: the ring of the Nibelungs)
-You beated the monsters and broke the curse? Good, now you have to find some place to actualy spend that money, because by the DMG each city has a limit on what it can sell to you, and no matter how much you insist the farmer village by RAW doesn't have stashes of magic weapons and scrolls to sell you.
-Insert rust monster/babau/steel predator ecounter. Yes, just like there's monsters that can give wealth if the DM's feeling generous, there's monsters that destroy wealth if the DM feels like the PCs start geting too much!
Also, what happens if we replace "coins" with "souls" or "raw chaos" or "major artifacts" on the cave? Does your campaign world needs caves bursting with shiny stuff at every corner? Then I guess the dungeomicon would work for you, but personally I'll rather have caves full of valuables to be extremely rare sights only reached after a lot of hard work and sacrifice.