Certainly not defending his product, but many of us pay similar prices for HPL. The difference is we know what we're buying relative to Dave's "trust us" oil.
I have never used HPL but I have looked at there products and they are very clear about what they are offering, and even willing to answer questions about it, specifically because they blend it themselves. If its what you want then I understand exactly why people would buy it.
To me, the biggest take-away is you buy HPL for its quality "ingredients" and extended OCI abilities, especially when driving a diesel. Dave is marketing his unknown product, but requires oil to be changed every 3k miles on his rebuilt engines or your warranty is void. I wonder how many of his engine rebuilding customers are aware of these limitations before having their engines rebuilt by his shop? At 3k intervals, I'd be buying the cheapest swill that "meets the specs". After the warranty expires, switch to a high quality oil designed to be driven extended intervals.
That's not wildly uncommon in that industry. Jasper requires oil changes every 3-4 months or 3,000-4,000 miles, whichever comes first.
Yes, it aligns with the Klotz SD-1 (severe duty) product line of diesel oils. It's priced accordingly also.
I could see 5k intervals. 3k does seem excessive but I guess it removes all risk depending on the condition of emissions systems and DPF regens (3k pretty much guarantees any fuel dilution likely won’t kill the engine as it’ll be changed out quickly enough).
Maybe, but some of the @High Performance Lubricants product could get to that point. Im not against paying
if its good oil, fits a specific need like high tbn or hths. If its 75$, does 10k on a TGDi engine, doesn't shear out of weight, and could possibly give me margin to go another 5k thats not too bad. 
