Note that I am in the slab business so I my opinion is not without bias but I will offer it anyway. Using granite tile IMHO is half a step up from ceramic tile in appearance and you still have the grout lines to deal with…. which in my experience is the number one reason my clients remove the existing tile in the first place.

Granite tiles do not look anywhere near as good as slab granite. While you may not get 100% of your investment in slab granite back if you are installing it in a house to sell you WILL make the kitchen much more appealing than graite tile.

12K for a kitchen sounds quite high to me unless the kitchen is very big or they have selected a very expensive material. My average kitchen runs between $5-$6k including demo of the existing tops. We import our own stone and do not sub any of the granite fabrication or installation, it is all in house.