What's being engraved? Text, logo? Do you have artwork?
I have a laser and have spent a good bit on upgrading it but still $20 is a bit high...
There is laser tube time (tube's don't last forever so it's a hard cost) but the rest is pretty soft. If I had to do the prepping of the artwork and it was the only thing I was doing, maybe get somewhere near that. But if that was the case, I'd probably send them somewhere more economical anyway.