I guess you might have overpaid, had he used your (E-Bay) mast and it did not work properly you would have complained. Any one who takes on a repair after the customer has been in it, deserves to be paid more. Why did you not get a total antenna from (E-Bay) or go to Pep Boys and squeak about making it fit.
I dont know where you got a $300 price, a mast at MB is over a hundred these days, and they gave me a so called discount