You're making an illogical association. The cost of the regulator has nothing to do with the cost of servicing it.
You spent $250 on a regulator and somehow you want the labor and parts for your bargain regulator to be less expensive. Why?
Should a technician charge less per hour or not be compensated for the parts they have to buy to service your regulator just because you shopped a deal?
If I bought a pair of several hundred dollar mens' shoes at a thrift shop for $10 and they needed to be resoled, should I get a discount because I only paid $10 for the shoes in the first place?
If it's not worth it to you to service your gear, sell it on the used market and buy new every year. Otherwise you pay for the service that you don't want to pay for and don't know how to do yourself. The cost of the regulator is completely irrelevant to the technician who would work on your gear.
I don't think he's asked anything illogical. If the cost to replace is about the same to maintain, then it's a justifiable question as to what he should do. So do you have any recommendations on what a regulator service should cost or do you only know what shoes at a thrift store cost?