Yes, he made a lot of money. The filament to make 100 comedy-grade lower receivers (not actually safe to use for more than a few rounds but good enough to fool a government clerk), is about one hundred bucks. The time to take to print that comedy grade receiver costs maybe a dollar per receiver on the upper end for electricity, and maybe five bucks per for checking in and babysitting the start of the print.
On the other hand, with new ATF rules (which are unconstitutional if we held to precedent but unchallenged in court and who knows what the Supreme court will look like when it gets there) his stunt could turn him into an unlicensed firearms dealer and treated like a terrorist by the ATF. Guaranteed, he is on a list now. Not sure what list, but it would be surprising if he doesn have problems getting on an airplane or doing his taxes for a long time, much less actually purchasing a real firearm if he so desires. If the deep state hates anything more than someone showing their incompetence to the world, I have yet to see it.
Fully expect that this is the route the government will take. They will use it as a threat or to make an example of him, probably the former.
He'll likely be told to return the money or he'll be prosecuted for a myriad of gun-related offenses and given what he did and the complexity of gun laws, he probably violated the letter-of-law somewhere along the line or close enough to at least secure an indictment. Someone from the state AG's office will likely contact him with a proposal - return the money or we'll prosecute you and you will definitely accrue far more than $21,000 in attorney fees while facing the possibility of a conviction, fines, and imprisonment.
He should have kept his mouth shut, although I don't think this was ever a good idea.