Why increase weapon's npc price?
Well bcs it seems there is way too much of some types of weapons compared with the number of players who might buy them. Hence prices are dropping very fast and dungeons appear not to be worth the seekers. Since it is the main way to get money for many people, i believe it doesn't help players to stay in the game.
What i suggest is to rise weapons'prices to like 500gold*item lvl for purple ones and 250/300*lvl for blue ones. This way if u drop the 20th 2h spring axe of the server but no seeker is willing to buy it, u won't get pissed off trying to sell it before prices drop or selling it for peanuts.
This way we would be going in dg thinking that in the worst case at least we could get our money back, since catas price would rise too (ofc craft weapons prices should still be lower than the price of the licenses used to craft it)
And rare weapons will still stay expensive. +it would bring more gold in the game, and basically the more u play the more u get, quite safely. And more money= more amp.
Same thing could be done with armors and relics (#relic that regenerates a bit of mana when killing an ennemy).