Bahahah @ the OP. You my friend have industry blindness from too much trench time. Everyone who isn't a GNU'nerd is suspect to clicking on spam. Heck I get spams all the time from my non technical friends. Has their name and all on the spams. Easy to fall for the bait, especially where you aren't suspicious of everything and distrusting naturally. (shh quit making fun of me).
Spam = money and lots of it. That's what SPAM is all about. Nothing else.
Sure you need to send many millions of spam per day. Yes, the actual buy rate from such is low.
You also have spammers who are selling counterfeit goods and those selling illegal goods (i.e illegal drugs). Then there are spammers who are running fancy identification theft rackets...
A small scale spammer is going to be pushing < $1 million a year in sales (doesn't take long to ramp up to that ceiling). Rates for him are likely high on IP, servers and whack a mole with constant server setups and long hours stringing the bullshit together. He might be spending $200k a year on server and related costs, most spending about half of that I'd say.
Larger outfits are even more profitable.
A $3 VPS is just one of MANY machines in a spam operation. No real spam operation is running things off a VPS since all those spams create server issues and such an environment should have caps and monitoring in place to regulate such fun.