I'd sooner spend money on glass than any other mod. With our lighting environment, that glass makes a big difference. Totally worth it, IMO. Lots of times I've had to reach in to see if the glass was actually on the machine or not, because there was not enough glare to tell me it's actually installed. Yes, I can find angles where I still see glare, but.. I have to look for them now.
Got 10 sheets on the last sale. Shipping to California for me added about 15% to the price, UPS ground. Very well packaged; no damage at all.
Overpriced? Probably. Just like any other mod. Just like the pinball machines themselves. You won't find this stuff cheap on craigslist. The only real way to get a deal here is to find a special like Jen's posted - and try to amortize the shipping by getting two sheets instead of one. Or look at some of the alternatives.