"Repairing a sub floor" really sounds complicated and expensive - coming from the mouth of a contractor.
Its plywood
If you are re-doing the entire kitchen, and flooring... you tear everything out... you cut out the bad floor, plywood + hammer + nails - you just /replaced your sub-floor/ -woohoo. Just go floor joist to floor joist - and you don't have to work about adding braces or anything as if you were just trying to cut out a small part.
Now obviously there are tons of other factors, like why was it rotting - was it just leaks throughout the years from the normal plumbing issues here and there... is there something bad under it? It is not level? Then there are other factors.
How big is the kitchen to get to 60k? Sheesh- I have not watched any home shows lately - but while I had my wife at the ER they had on "The Flip Off" - and the one dude and his wife spent 100k on a kitchen and that was super high end & everything custom, walls moved, and the attached dining room + fire place + walls - all flooring- etc etc etc and in CA and "uppity up" ... so 60k to me is insane, even with Appliances.
I just got a complete kitchen appliances as mentioned earlier, all LG -$2,600 - French Door Fridge, Induction Range, Dishwasher and Over Range Microwave. Got all spooked by the "LG compressor" thing so I bought the extended warranty, so that added like 200$ or so.
Anywho - along with new stuff, I have designed an entire new kitchen - Ikea designer has it at 8k and I got a quote from a kitchen remodeling lady - 13k - an that includes some ceiling work to re-texture as I would remove a drop down ceiling (yay, the 70's....) - the difference between 8k for "the stuff" from ikea and 13k for her to do it... 5k... I can put in a lot of work to make up that 5k... anywho... I say, get more quotes, like at least 3.