Listing on a Top exchange is not a free job its obvious that they do charge you.
Listing on a major exchange costs, sure, but there are plenty of exchanges out there which will list tokens for minimal costs or even free.
Now thinking on the other hand the spam project gets a website done, whitepaper, content, promotion, listing blah blah blah and all of it comes for a cost.
All of this can be done for free. Websites, whitepaper, and content can all (and often are) plagiarized or copied from various places. Promotion is easy - you just pay people in your new token that you just created out of thin air. Spammers will work for any old piece of trash, and doesn't cost the scammers a cent.
One would spam only if they are getting profit, right?
As I said above, you can create, launch, advertise, and list a scam for essentially free. It only takes a couple of idiots to buy these tokens and the scammers have made a profit on their time.
Just image how many investor might be there getting chopped with such spam blades.
There is no end to people who will believe any old rubbish are easily parted with their money.