price to drill and tap

[apprentice]

what is a fair price to drill and tap a 141 for a receiver sight? I am ticked, I found a new in the box Redfield 80 series sight for my 141 and took it to the gunsmith to have the receiver drilled and tapped, he quoted in writing $30 a hole and now wants $125 (in cash) for the job for "unforseeable difficulties.