I have not paid to have other people reseal my tile. I have done it myself twice. The method I used was to clean it very thoroughly (this included going on my hands and knees to get out all the junk) and then paint on the re-sealer, letting it dry and painting it again. I think 2 coats was plenty for my floors (which are only about 10 years old). Most saltillo is sealed before it is installed and should only need a touch-up in worn areas. I've re-sealed the areas we walk on in the kitchen more often than the rest of the house. I don't know about restaining it? I've never heard of that process. I think the cost would depend on which area of the country you live in but I would say that both prices you were quoted sound a bit high to me. I think I'd ask for references.