I don't necessarily have this problem so take my thoughts with a grain of salt but I've recently started viewing job costs as "this is what it takes for me, my team, and what we have in our arsenal to get this job done". If a customer doesn't like your bid because it includes making a profit on an overpriced supplier, so be it.
This would be a problem I would work on as a side project but I wouldn't stress out if you can't solve it this week. This would be like a handyman working in Los Angeles with crazy traffic. If someone calls you in from across town and wants a job, you'd have to charge for gas and some time because it's going to take you forever to get there. If they think that's too high, then it doesn't make sense to do it.
I'd rather sit at home and make no money then work all day at your house and make no money. I think your problem kind of falls in to that. Maybe the solution is to build value in the products to your perspective customers and convey why you have to charge more.
