Well I worked it out and I'm definitely not doing

seeing as dragon bones are the only bones anyone would ever be wise enough to use to get to 99 prayer (you don't see zezima or duffy using big bones/bones for 99 prayer lol) it would mean this (for me):
-Level 53 - 99 Prayer
-12,892,143 XP to go
-179,058 dragon bones needed (2,353 per bone brings total cost to: 421,323,474gp)
My question is: Why don't people use ourg bones? 140 experience, double dragon bones, I would only need 92,087 of them. But then...I saw why, 14,400gp PER BONE, crazy stuff! That would cost 1,326,052,800 (almost 1 BILLION more!). I am still, however, confused, go to the GE database on the runescape website, and there are two 'Ourg Bones' (
http://itemdb-rs.runescape.com/viewitem.ws?obj=14793 and
http://itemdb-rs.runescape.com/viewitem.ws?obj=4834) very confusing any ideas?