That was the one thing that really stood out for me. I've seen petroleum jelly recommended by people who should know what they're doing because it had the same melting temperature as the original lube. Nova says it makes a sticky mess inside the machine. She also states that many old manuals say not to. She could be right, they could all be right. Conflicting data isn't that hard to find in the sewing machine world.
I only have one machine where I put petroleum jelly in it and it hasn't been there long enough and the machine doesn't get ran often enough to really give it a fair test.
I'm not ordering any any time soon (financial reasons, nothing against the product itself) but from what I've seen of other products the price doesn't seem terrible when you think of the cost of getting it made or at least repackaged in small amounts and it sounds like she put in the effort to find a good product. A little also goes a long way so a tube is likely to last a while.
I don't think she plans to retire off it, I think she is actually just trying to provide a good solution to a known problem.
Rodney