They go for around $1,000 new on Agon all the time...
I don't actually own one, would like to at some point as my voltage reads about 123V all the time. It doesn't fluctuate though since I installed a dedicated circuit for my gear.
But I've seen them in use many times. It'll easily keep up with your voltage spikes & dips.
I'd make getting one a higher priority for myself if I had voltages fluctuations quite frequently. But other than my voltage being a bit high, I don't have any other real power problems.