I got some real plumbers out to the house, and it the bill was $914 because of Roto Rooter. The part that they came back to "fix" leaked and the tub still wouldn't drain so I had to get someone out there. They removed the old plumbing and put in new, primarily because it wouldn't take them any longer to do that than just replace the one part.
When they finished that, we found out that the tub still wouldn't drain. Turns out Roto Rooter hadn't properly snaked out the drains. So, someone had to come back and do what Roto Rooter claimed to do all over again.
So, the upshot of it is, Roto Rooter should pay this bill. They are still liable for breaking my plumbing. I'm not sure what I would have paid if they were actually competent, but considering the time I had to take off of work, the effort it takes to get them to actually listen, not mention the costs- like the $32 dollar stop payment on the check, I think they should pay the whole thing.
Any professional knows he can incur a liability larger than what he expected to be paid for; that's why people get bonded.