You can't forget that RuneScape, in its bare form, is a business. 2 million paying customers monthly is hard to argue with. By offering these great deals for members it would boost their already phenominal profit margin.
im 99% sure this wont work... but does ectophial have only normal xp? b/c thats not really a mini-game, nor is it a quest reward... it it is double xp ud be getting 6x regular xp per bone = ridiculous.