Your blindness is showing. I know people are going to crap all over me for this, but.....
OK, how did the Clintons, Obama and Biden go from relative poverty to net worth of tens of millions of dollars (with Biden being the piker)? BY SELLING THINGS!!!!!!!!!!!!!!!!!
Hillary said they were dirt poor when they left the White House, Obama said "...at some point, you've made enough money". Biden has sold books, they all charge a buttload for speeches and if you look into it, Biden recently took in more than $340 Million in campaign contributions. BTW- book deals come with a huge advance and there's really no cost to the person whose name is on the cover but the hats and other merch cost the seller. That's a big difference.
Monetary gain, for someone who didn't take his Presidential salary? GMAB! Show me another POTUS who ever did that.