She does explicitly go on to say "by Hollywood standards"

I honestly saw it was $15million and figured that's a bargain for the estate of one of the most esteemed directors of his generation. Relative to his level of fame and respect, his monetary assets do seem low.

But then this certainly matches the public perception of Lynch. He made the things that he wanted to make, not the things that were guaranteed to sell. I'm sure commercial success was important to him, but there were lots of paths he could have taken that would have lead to a lot more.