This is really nice. To the author though, I think a price revision would be in place. Keep free and the $45 option but change unlimited to $500 and resell to $1000. I think you're undervaluing your work as a product.
> There is nothing that prevents people from deciding to pay him more if they feel like it.
That's a fallacious argument. That's not how the market works—consumers are very biased by prices. The more something costs, the more the perceived worth. That's why retailers offer sales. We've priced this at $1000 because it's worth $1000, but we'll give it to you for $800! If you price something too low, you're saying: this is worth $600, but please please pay me $800 because I worked really hard!
I agree with grandparent. $400 is at most 10 hours of designer/developer time—orders of magnitude cheaper than having this custom coded. The current Django admin desigin is a few years out of date; if I were developing a large-scale commercial application, I'd be more than happy to drop a few grand to significantly improve the backend UX.
I think the price is reasonable and encourages people to use it in their commercial Django projects.
There is nothing that prevents people from deciding to pay him more if they feel like it.