If you take the price of a custom made folder and divide it in half, then you've got a Grip with custom made handles, pretty economical. Benefit #1.
Since the Axis lock is unavailable in all but the most expensive folders, there's benefit #2.
Benchmade's heat treat, materials, and fit and finish are reliable and generally very high quality, maybe more so than some custom folders, benefit #3.
Will the upgrade enhance the resale value of the knife? Well, probably not. It's meant as an 'experience enhancer'. I think the guy who's going to spring for this is probably unconcerned with resale value, and more concerned with having a cool, relatively rare, aftermarket upgrade, to a factory product which has an excellent track record.
That's my two bits for what they're worth.