Craigslist has a running cost of practically nil when you compare it to most tech companies

Listing some sorts of items costs money. I recently sold a used car and had to pay them a small fee.

Really? I was unaware of this change, haven't sold a car in a while (but have sold several on CL in the past).

I guess the spam level got too intense, which I can definitely vouch for. Lots of not-believable deals that were basically phishing scams.

Job postings cost money too. They definitely rake it in!

Some ads carry a fee. A full listing here:

https://www.craigslist.org/about/help/posting_fees

People pay to post prominently-placed ads.