Man I was thinking about this myself. Im sure one thats actually been in the octagon is worth pretty big bucks. I actually work in a graphic/media shop and just a normal banner that size can range anywheres between $400-$800 depending on colours and resolution. No joke the shit is expensive.
I was considering just making one for a favourite fighter and hang it on the wall in the smoke room, but even with my hookups it'd still be too expensive for my liking. Like $200 minimum, me doing all the work on my spare time.
One thats been in the cage has got to be worth an easy $1000. But I guess it all depends on where you live n stuff.
God hates me, never keep my banger on safety
My mother raised me alone, you can't break me
Like my hearts pumpin the blood of Royce Gracie! 13-4-1 in sig/av