Did anyone think to ask for an estimate, guesstimate, price per hour
and/or anything in writing?

No, not for what should have been a trivial job. For a big job, sure. For
a little job, no.

Its kind of hard to argue after the fact when they have already
completed the work, you paid them and then you go back and cancel the
check.

Excuse me but who said anything about cancelling a check? Certainly not
me. No one is cancelling a check or even asking for a refund.

I take those kind of checks straight to the
county prosecuting attorney. Thats what they are for.

Fascinating but completely off topic.

Should she have asked for estimates first? Clearly yes since there are
plumbing contractors out there who charge senior citizens almost 500
dollars for what was likely a 150-250 dollar job.

Water under the bridge. But you're wrong if you think I have no business
even raising the question. If someone walks through a bad neighborhood in
the middle of the night flashing a lot of cash and jewels and they get
robbed you can fairly call them foolish. But that doesn't make it any less
a crime. (Only an analogy; I'm not saying this was a crime. Just in
spirit.)