I recently had to exchange a five pound bottle that was due for recertification. I had been getting it refilled for about $14 a pop at a local place.
So I took it to a local Air-Gas supplier for exchange for a newer bottle. The cost was $29. The dealer said co2 costs went up four times during the past year. My advice if you are close to needing co2 or a newer bottle get it now before costs go up even more.