The kit itself isn't too bad, but contractors will kill you. Realistically you want water, which means a below frost line trench. Electricity, which means buried or overhead lines and a new circuit, subpanel, grounding rods. Heating, which means either propane tanks, natural gas line, or electric heaters.
If you're gonna grow perennials over winter in-ground, you probably want an insulated foundation, which means an insulated stem wall that goes down below grade a couple feet, which means excavation, concrete forms or masonry block.
I could easily see this running 100k total to "do it right" if you hire out everything.
The cheapest route would be to build a foundation of something like railroad ties/big pressure treated wood or some concrete blocks. If you grow in containers you can get away with uninsulated ground/cold floor. An extension cord or some fat romex or ufb for power... run across the yard from your house. Heating depends on your fuel source. A problem you'll run into is with water. If you just run a garden hose it'll freeze solid in winter, and then you will be stuck running bucket of water from house to yard. I have been through all this with my last house/greenhouse.