$20k/month is $240k/year, which is some serious money. Forgive me if I'm a little skeptical of these numbers.
1. $20k/month every month? Unlikely.
2. Self-employment taxes + other business expenses.
edit: formatting
A lot of startups in the sharing economy space have been guilty of grossly exaggerating how much their contractors/employees actually make. Is this just yet another instance of that or are these numbers legitimate? I think that's a perfectly reasonable question to ask.