Sure Grips are funny. Becuase they have to slip around corners, some wear is expected and designed in. Knowing that, I would suggest for every build use the best SG you can afford. I consider the old clutch type SG to be the least expensive base model but figure on rebuilding the clutch unit. The Auburn setup is a cone type. That is a disposable center section. The steel on steel wear surfaces slide very time you corner. And hard cornering will result in much faster wear. All the particles of steel stay in the oil, and so they get run accross the gear faces too, and all thru the bearings. ONce they slip the first time, the clock is ticking on them. I will run them if I'm told to, but They are designed for so much wear, then throw them away. The True Tracs have no such wear. They hold like a locker, but slide very smoothly in turns. It is the best street/strip limited slip out there. And between $1-200 more than everything else. As far as cost, the last re-gear I did was on a factory tight (low miles, in good shape) cone type. The ring and pinion, bearing kit, new ring gear bolts, and oil/gasket came to just shy of $400. I added a new yoke with Dana 60 style U bolts, that was another $80. All parts from Dr Diff, and with my labor after assembly and detailing came to just shy of $700. Randy is charging you for the new Auburn, so with that, it would have been $1080. But he gets $1300 plus core and freight. You could have a local shop buildit with the True Trac for less $$, and have a place to bring it if there is an issue. Randy's is an easy call, but a little high for what you get IMO. But that's just my opinion. Every driver and situation can be different. I want to know once a job has been done, I will only see that customer for another job..Not because something wore out or broke prematurely.