How much of deposit should I keep for damage to flooring

[Tom Rychlewski]

I have a house that I put pre-finished hard wood floors in about 3 years ago. My latest tenants dogs (2 labs) completely scratched the floors. I called a few companies to repair and they say that because it's only 150 sqft I will have to pay a minimum cost of $500. That covered buffing or sanding and refinishing. They also say that by sanding and refinishing I will void the manufacturers warranty.

The floors look terrible and I don't want to void the warranty, I also don't want to be unfair to my tenant either and make them replace the floors all together.

What should I do? Can I charge the $500 minimum to refinish 150sqft of flooring (seems high but I'm having trouble finding people to come out for less)? Should I just forget the flooring warranty?