Zoo quest mob ! it is a boss kind of like a colossus Edit: ALOT more rare considering you can only find these mobs in the zoo quest, while you can farm t2a titan valley and have the chance of colossus appear more often
I paid 1.75 for mine if memory serves and that was including a friendly discount. That was a pretty long time ago. But appears it's only up to 7 of them at this point, so it's a fairly slow drop.. at best I get 5 chances at one per zookeeper depending on respawn, most of time just 4 chances a run at the 1/250 chance. What I paid was a private sale from a friend and it was valued low towards trade in of something I had they wanted. Your milage may vary, I'd say 2m is in the ball park easily though.
