Yes, it can certainly be less expensive to rent a reservation from a DVC owner than booking directly through Disney.
But, one does have to be comfortable with it as there are differences. First, you are entering into a private transaction with a DVC owner and not Disney. All terms will be up to them.
In addition, they own the reservation until you check in. Be sure you are completely comfortable with this. While it is rare to experience problems, the owner could cancel it at any time with no recourse really to the renter.
The cancellation policy is usually more restrictive than with Disney and you don't get daily mousekeeping, including new towels with a
DVC rental.
Of course, the huge benefit, as you have discovered is the savings if there are no current Disney discounts that bring down the rack rate of the room.
It can be a great deal but definitely one in which the renter needs to be comfortable with the entire process!!
Good luck!