Its not that gollux equips specifically have gone up in price, its more of a server wide mass inflation that has pushed up the prices for everything.... It just happens to be more noticeable in items that had a conrete-ish price prior to the inflation.
with the gollux equips that you buy with coins, each one can only be purchased once per char.
so once you buy all the rings and stuff, cant get more unless you do gollux on another char.
so kind of limited supply