M14, let's get back to the original issue: why is it going to cost $100 to have it drilled and tapped? You could probably do the job yourself- the only way you could screw up is if the spacing is off. What I have done is to find a tube (hobby metal- ACE hardware) that fits inside the tapped holes in the base. I then "tack" or temporarily glue the base in place and drill the holes. They should be dead center. These may have to be expanded just a little with the proper drill for the tap but generally you'll be right on the money. You'll need a regular tap and a bottming tap.
Question: what about one hole drilled and tapped and the other hole with a steel pin and everything epoxy glued (putty type epoxy) I've never done it but it might hold. If it would hold- that could be an option if you screwed up on the spacing for the second screw on a base.
And........
I've never done this, I always knock off the base after drilling with the tubes and then tap but I suppose you could tap one hole, put on the base and then run the tap down the threads of the second hole on the base and right into the second hole you drilled- that ought to cut a perfect tread- alignment.
Anyone ever do it that way?