First of all, I would caution you and anyone else hiring someone in the
future to come to a very specific agreement about what is and is not
covered, paid for, expected before research is done. If you asked for
Ignacz Kaufman's death record in 1901, for example, that would be
great-unfortunately we sometimes don't know that specifically and have to
ask for a search for Ignacz death record whatever year. If you don't
specify, and especially with a name which you know to be pretty common (the
researcher may not know that), he might copy every Kaufman record thinking
he had found you a treasure trove.
It is customary to pay for travel and hotel costs; unless you specified
sending receipts, then you pay whatever. Travel is not easy or convenient
in many places.
If you paid for translation, I would expect translation of the document.
Again, it depends on the agreement, and whether he said his English is good
It seems like you asked the person to get information on Ignacz Kaufman
specifically. If so, then I would not feel it responsible for paying for
any documents which are not somehow related to him. If you were not clear
on that, then you would pay. If you hope to get anything else in the
future, you will pay him well for what he has done.
Since you have the documents and haven't paid yet, I would suggest writing
to the researcher and suggesting a compromise. You should end up paying
for the search and the travel, but I would think there would be a
compromise on the 'translation' and possibly the documents which don't
relate to Ignacz.
Finally, for the sake of all genealogists, be diplomatic! We all want
better cooperation with people we will possibly want to use in the future
(unless they are outright crooks, and this one sounds like he did much or
most of what was asked).