Amazon is an outlet for Cleveland, Chicago Latrobe, and many other quality brands as well as mountains of junk and counterfeit items. Grainger breaks it off in your A$$ on both price and freight, especially if you don't have a business account.
If you really wanted to be Mr. Superior Knowledge and Advice you could recommend buying through Grainger's sister company, Imperial Supplies, where you can talk with live sales reps and get your prices....and freight....significantly reduced.
Drill Doctors at below retail price are probably "refurbished" (returns that still mostly work and have most of their pieces).
The 750X is a big improvement over the original but don't be fooled into thinking it performs as advertised. The split point feature is poor at best and only works on a narrow range of bit sizes. Even then, it leaves much to be desired so I split mine by hand. The ability to sharpen different angles and adjust predictably for different helical twist rates is nice but expect a big learning curve to using the machine.