Is $4,700 to prep uneven subfloor before laminate install a fair price?

I plan to have Inhaus Lamdura laminate flooring installed in my 1973 one-story house, which is approximately 800 sq ft. The plywood subfloor is very uneven, with up to a 1-inch differential in places, which was beyond the scope of the floor installer. I'm seeking a quote to address this issue. I'm concerned about the reasonableness of the $4,700 price for eastern NC and if I need to clarify the scope of work, such as the specifics of concrete footings, the target subfloor tolerance, whether the work fully levels or just improves the subfloor, warranty details, and if recheck/fine-tuning after settling is included. The unevenness is widespread, likely due to supplemental supports added after initial construction. My budget is small, so hardwood and tile are not options. I'm also considering renting the house out in the future and am worried about upkeep.