As much as the Octos are quite cool, from most of my reading your extremely lucky to have one that lives longer than 2 years anyway and have to build an escape proof tank and constantly provide interest for the octopus (putting food in in jam jars is one).
They are a huge expensive outlay for a short term pet.
Yeah, the longest living Octos rarely live longer than 6-8 years and the average is less than 2 so the cost and maintnence for one is outragous IMO. Still, what people spend their money on is not my concern.