1)The pan is reparable in place w/ heli-coil or insert (pour a quart or 2 of kerosene through engine to flush any aluminum bits out the drain hole)
2)A used pan can usually be had for $35-$50 at most.
3)The pan can be replaced w/o jacking the engine (unless your engine mounts are badly sagged)

You might consider checking around for estimates next time. Your mechanic may be a tad high.

ALWAYS hand thread the drain bolt in finger tight with the fingers before tightening it.

Bob
FYI: I recently replaced my stock plug with a magnetic one bought from ALL BMW Discount Parts, and consequently lost the use of my drain pan.
Admittedly I did cross-thread the bolt after changing the oil, but I've never done that before, making me think the new bolt was of a softer metal than the pan.
Problem was, there's only one spot on the pan that's low enough to sufficiently drain all the oil, and it wasn't possible to re-thread the original hole due to it's location, so I had to replace the entire pan.
The entire bill came to $250 for a used oil pan, and about $200 more for the installation, since you have to lift up the engine for the procedure.
Point is, watch out for the quality of new bolts, and never cross-thread when changing the oil! It's a pretty high price for a little mistake.