Does the tiny house trailer come with the insulated subfloor already built on it and included in the price?

No it does not. When Fred demonstrated how to build the subfloor of the tiny house using the Floor-Joist Tie Downs and the Stud Wall Tie Downs in a trailer video, it was to demonstrate the construction method of an efficient and well insulated subfloor. When you buy a trailer from us you get the chassis only and the floor construction is up to you.