I mean, if you're so overpowered, why do you even want to buy anything better? The economy's working just right for you, if you're doing well in terms of gear, isn't it?
After you leave fort joy, the economy/trading factor died because there's really nothing to buy compared to the last patch.
The new patch, I had to wait until they restock before new gears appear and even then, I still end up wearing bleh ring or necklaces because majority of the purple stuffs are gone from the store.
I wasn't even using up-to-level gear when fighting around the end portion of Act 1 compared to pre patch where I bought a bunch of purple stuffs from the seekers to get some extra power. It was just Haste + Rage + Adrenaline + 2H/Bow being so ridiculously broken that I was still able to rekt it.