Hi we did the tubing 2 years ago and we loved it. Its a lot of fun (better than going down in a long raft - although that is more romantic).
I don't remember the cost but it was worth it. I don't recall it being far from Ochi (maybe 20 min) - it was basically a half day trip. I highly recommend changing into dry clothes before you head back. The air conditioning on the bus was cold.
We are going to CSS in January and will either do the tubing again or I want to try kayaks down the river next.
Go for it - have fun.