@SIPengineer - To be honest it sounds like you don't actually want the great advice others are giving you here and already have it in your mind that you are going to do this for way too cheap. Charging 80k a year with them doing say 10k units a year at a sale value of $600,000,000 and probably a profit of 30 to 90 million (assume 5 to 15% - maybe even more) is just a bad deal for you.
As other have said, ask your insurance what they would charge if you take on that amount of liability every year, I bet you will find a large portion of that 80k will go to the cost of that, then factor in the time it will take you to seal 10k projects a year (assuming you aren't just rubber stamping them - which has ethical concerns because of the potential for them to change something and you didn't notice), maintain your licensing (personal and business) in every state and any other misc costs associated with this endeavor.
I agree with phamENG on the fee arrangement, but would probably tweak it lower based on volume, maybe $350 to $500 reuse fee on the low end, this would cover profit, time to review and seal and any other admin time. Also remember, each state has varying statute of repose and you will need insurance that covers these well after they stop sending work your way, so a portion of the profits on each one of these also goes to future insurance.
Maybe another alternative is setup an arrangement with them that they cover your insurance costs every year and have to pay you a retainer amount up front to cover a tail policy, but I still wouldn't be happy knowing I made someone else 30 to 90 million profit a year and only got 80k of it.