They use Swish: https://sverigesradio.se/artikel/hundreds-of-suspected-cocai...

And again the same question: I have a friend who had to physically go to the restaurant to get a confirmation that he in fact had paid about $250 for dinner for six people and they then swished him back. How will you explain hundreds of transactions a month when you don't even have an official source of income?

Yes, but I mean it should presumably be very hard to even spend the money for the sellers here, let alone to launder them, which will be needed if you're selling all the time.