I've noticed that items cost more to upgrade than the cost of the item itself. For the more common,low-ranking items this is okay but it is daylight robbery when it comes to higher-level ranking items,especially the legendary ones. Prices can reach up to the 10,000s,I think it would need a lot of effort on the player's part to tediously farm the levels to raise that kind of money.
Also,just a slight digression: how about using a different colour or font for the legendaries? That would give a sense of satisfaction to the player. I've seen this before in other games but could it work in Last Legacy?