Me too.

Equiping a hero with basic armour (at least, a shield and a helmet) should not be so expensive, and more in the early game, when gildar are so scarce.

I don't think you're meant to just buy all your equips, that would make the adventuring part of the game seem rather meaningless. Hunting, selling loot, buying armor... to be honest, I think it's a pretty good balance atm.

I usually build my heros with no weapons or armor and just buy it, it's cheaper and reduces the build time.

I agree with this. It's fun to be able loot something you can actually use. If you can easily buy a complete set--even if it's just leather--then most of what we loot early will just be stuff to sell to a vendor.

You can find far better loot than leather armor. Being able to afford a full set of leather would in no way reduce my desire to loot everything I can find. It would make early game lairing easier though so perhaps that's why they don't want us running around in leather right away.

I think that the high prices of regular equipment solved several problems from a game design perspective.  For one thing, it made common loot more valuable.  When you quest early, and find a pair of leather bracers, you're actually happy.  For another thing, there was a quite serious problem in earlier versions where all your heroes started to look exactly the same.  This was at least partly because they were all equipped with the best equipment that was available in the stores.  This problem, which really bothered me, is pretty much gone.  A little bit of weirdness about why prices are so high is a small price to pay for these important fixes.

The only problem is that there is no choice.  You just don't buy stuff from the shop.