60 cents per sf to clean and 30 per sf to seal
Use a solvent based impregnating sealer (if you buy cheap shit from Home Depot in a green bottle, you will be here next week asking how to remove the milky haze, you will spend countless hours with floor stripper and a grout brush and it will still be there and you will be hating life and saying "why didn't I listen to that guy on the Internet")
Or just don't seal it at all.
Tile is not that hard and you definately shouldn't be charging super premium prices on your first ever tile clean just because an experienced cleaner on the Internet told you that's what he charges.