I really do appreciate all the input from everyone.
However, IMHO what wholesalers (or any other other shop) charges should never be factored into a price, they buy in huge bulk
for material and ink... A place I used to work at paid $80 for a gallon of ink. If you can't get the price you need to
get after material and overhead for a product, then you don't need to offer it. There's plenty of niches in this this industry
that pays multiples of what standard sign projects do (not speaking about this situation).
Problem is the guys supplying all the materials. The only cost is ink and machine time.
We don't compete with wholesalers. But wholesalers will print on their material, hem, grommet, and ship it out within 48 hours for the most part, for less than this guy wants to charge a "sister company". I say sister company because it sounds like they both throw a lot of work to each other, and have a closer relationship that a wholesaler and their client has. So while you shouldn't try to compete with wholesalers... Obviously this is a bit of a different situation, and the OP knows it... or he would just go with his standard pricing, and not ask what others would charge.
I doubt the "Client" cares about paying for the banners, so sure... charge $15. It'll just be a transaction for him - he'll likely appreciate it. But doing him a favor and helping him when he's down will leave a lasting impression on him, and when your machine breaks down... you'll have someone to turn to. But thats just my opinion... We have lots of people who we send work back and fourth to, most wont hesitate to drop everything theyre doing and rush a job for us if we need it done, because we treat them right and do the same.
Building good relationships helps you a lot in this business... and spending $10 on ink is a small price to pay to have the situation stay on the back of this guys mind and be grateful for what you did. You never know when you'll need a helping hand.