The economics still work out, unfortunately. It's really, really cheap to send spam, so it only takes a small fraction of a percent of people who click for it to work out.

Also, not everyone has the same level of spam filtering as you might be experiencing. Imagine an elderly couple who still pays for AOL, etc. I have been seeing a lot of spam recently about "medicare open enrollment starts soon".

Spammers actually still make money if the spam lands in the spam folder, because people still look at it.

Also, believe it or not, there are actually people who buy things advertised in the spam folder and get legit product.

My understanding is it's actually declining as a percent of email sent.