Why is everything in runescape going down in value?

I have been fishing for a while and everything keeps going down, I remember when swordies were 500 gp and lobs were 350, now lobs are 99 and swordies are 169. I mostly fish to earn money but it is becoming really slow now. It isn't only the fishing industry thats suffering, woodcutting, mining, and basically everything is suffering too. Y is everything suffering? Do you think things will ever go up in value again?