Pick away!
You have legitimate questions/comments.
We have several in house list broken-down into hundreds of categories based on the demographics of the names on the list. We then test offers we feel would pertain to that demo to see the results, then when a list owner contacts us to manage their list, we get details on their list demos and then research the offers we've tested to similar demos and then run them to their list. We write up custom creatives for each mailing to make the offer as targeted as possible.
As for the commission percentage, 90% would be unreasonable. We are in fact enduring quite a bit of cost in sending out the mailings as well as dedicating our time to set it all up. We have multiple managers who help handle the lists, so this helps ensure not a day or week or month goes wasted without an offer being mailed and commission being earned. Many of our affiliates love just logging into their account each morning, checking their commission and then going about their day able to do other things then worry about setting up a mailing or two.