I told my wife "Hey, I think I need a spotting scope." Two weeks later, she scored a 20-60x60 at a garage sale for $20. Been using it for nearly 10 years now.
There is something to what Dregs says. If you're shooting at Kokohead, the farthest you possibly need to be able to resolve bullet holes is 200 yards. Most likely, your worst case is .22 holes at 100 yards. Either way, even a fairly crappy scope will do the job.
What I find really makes the most difference is the stand. The wind at Kokohead shakes my scope all over the place. If it's dialed up past 30x or so, it is impossible to see even .30 caliber holes at 50 yards due to the vibration. Holding it steady doesn't really work (my hands are fairly shaky). So, if I had it to do all over again, I'd look for the scope that came with the most solid stand.