That I am afraid is the proverbial “How long is a piece of string” question. There are so many variables! Would need a bit more info to help really like:
Type of Tile
Total M2
Where in the House
Type of Grout
Type of Current Staining etc
If just a few stains around the cooker and sink on say a porcelain floor then with a pre wet, deep clean with a Mono Rotary, coupled with PSRP Xtreme HDT&G Cleaner, Vacuum, Rinse and Vacuum again probably £10 M2 then sealed as well £15 M2
All guesswork based on the above