There's also the fact that the Indy drive was designed for Ilmor engines by the same people who designed those engines. So you're looking at a single-source (except for the prop) propulsion system.
How would that affect resale value? No one knows, because as I understand it no one has used this kit to retrofit an Ilmor engine and then sold the boat. And even then you'd have to compare it to the resale value of the same boat with the same hours and the same power (again, the retrofit kit, like the Indy drive, is only going to Ilmor engines at this time) and a Mercury drive.