I think the prices are fair.

The problem is you don't want to price them so high that you never get to use them until the very end. Not to mention, some of them don't offer as much as you think in a lot of cases (just the way how DMG and Armor works in TL2) and you take a pretty big hit on resell. So finding out the one item you thought would be cool and then going out into the fray and realizing it wasn't that big of an upgrade would be devestating at prices that are higher.

That could be mitigated if someone ever figured out how to compare your DPS and other stats on hover over a potential weapon/armor purchase in the store. But alas, I don't think that's possible given what's available in game. You currently just have to purchase it, try it out on the dummy or real-mobs, and then see what comes back in a lot of cases... resulting in some experimentation and lost gold many times...

@Addicted Gamer

I think you are correct. I have been playing on multiple characters with the Adventure Mart mod installed, and have only had the chance to buy about 5-6 items, and none of those were Legendary. You can't even start really shopping there until your level 10-15, and thats only if you happen to meet the stats requirements of something extremely cheap in the store. I think Prices stay where they are at for now.