Point is if i'm there with the pump already dis-assembled.. why would I put used parts back in and then risk failure. Shot gun approach, put it all new. Hard to tell rubber is going bad. Worse when something like a valve goes bad and pump doesnt build pressure properly. First rebuilds back 10 years ago.. just would change whatever failed trying to save the customer $$.. that was a fail. So once we started putting it all new.. problems resolved. Funny thing about parts from Shurflo, the cost of individual parts is exponentially higher than the cost of a new pump. Like buying a new car for 20K and you price it out parts wise its over 100K. So we are torn from simply selling new pumps or offering our customers a cheaper option.
Better yet, here are the numbers
Diaphragm/cam 42.18
check valve seal kit 9.26
valve is 19.49
Or get pump rebuilt for 80