Recertifying nitrous bottles?

Depends on the filling station. Sometimes they can’t get the filled cylinder full. If they charged you for product you didn’t get that’s a different story.
I paid $130 ($65 for each filled 10 lb bottle). I received 9.5 lb in one, and 7 lb in the other identical bottle done at the same time with the same pump. So it's the different story, unfortunately.
At least it was only at worst a $22.75 lesson on where not to go again.