The prices will only go up if wildy is removed. Its because the items are permanentely there, + with more put in every day from bossing that the items are crashing.
Well I estimate that they will go up but not much and this could be around the price now so they could fluctuate a bit more either way . The reason they are so low is because of stupid Jagex adding more great weapons . Remember the days when you had to be kind of rich to own one of these .