I noticed something strange, then you enchant lots of iron daggers the value goes down, no not then you sell many but the value displayed in the enchanting interface then you have made many.

Now the really strange part, if you wait some days with selling them price goes up and stay up. Then I learned banish, they sold for around 900, it went down to 600 and is now up to 900 again.

Has not seen that potions or smithed items has this effect.

I'm playing on PC and I have something similar as well.

When I first enchant some iron daggers they have a value of around 1700, and can be sold for around 600-700 septims. But if I close the game and restart it loading the save with already enchanted daggers, they now have a value of 3200 and can be sold for more than 1200 septims. However, newly enchanted daggers in that "game section" still have a value of 1700, despite they are completely the same as those enchanted before.

Also I found that restarting the game will also completely restock a merchant's vendor, both their gold and items will be restocked, even if you just took all of their gold 1 game minute earlier.

I think it has something to do with the amout of charge the item has left. Could be wrong though.

Its probably a remnant of the 'affecting the economy feature', which despite being so lauded did not make it into the game.

It appears to be a bug. Although honestly, it's not really a big deal in the high end of the scale. You can make quite a bit of coin with enchanting even if you're at 100 enchanting with several enchanting perks. Granted that doesn't mean I wouldn't want it fixed, I'm just saying that it's not that big of a deal.

http://www.uesp.net/wiki/Skyrim:Enchanting#Bugs

This makes sense, it's either part of some economy function but more probably that the enchantment table calculates the price wrong, it's not the number of items sold who set price but your enchantment level, as you level up the price goes down.
Then you save and reload I guess the price of the item is calculated as other random enchanted items. base price+ enchanted effect price+ magic charge.

Ty for the save and reload to restock tips.

There are perks in the Speech Tree for this.

When you invest in a shop and increase the shopkeepers gold and get the shops to buy other items than they normally do, that is effecting the economy.

You know what I meant.
The whole destroying a lumbermill to damage the economy, work at it to help it thing.
There are remnants of it all over the game, but they are not joined together and some of them dont do anything.