Exactly the same thing happens in bitcoin system. The senders are just transferring data (numbers) via bitcoin messaging system, without the receivers getting the ownership rights on some type of property. The receivers are just able to read the received numbers or send them to someone else. And that's basically it. That's what messaging system are doing.
Ok, let's do a test.
Get 1 BTC, I'll give you my address, send that Bitcoin to my address and let's see afterward who owns it and who can send that "SMS" once more or if you can get that "data" back unless I want that too. Deal?
That essentially means that there's no buying going on in the bitcoin system. No investing. We don't buy or invest in numbers. This would be as nonsensical as saying that we bought or invested in SMS message when we received one. Receiving a dozen of letters or numbers is not investing or buying, because alfanumeric symbols are not copyrighted. We use them for free whenever we need them.
Again, can you please send me some let's say 10 BTC, maybe 20 BTC if you're such a nice guy? Especially since they are free?
If we need numbers for performing mathematical calculations or labeling and quantifying things, we just produce them out of thin air and represent with symbols (0-9). We don't need to buy numbers. We don't need someone to protect them in a distributed database. Numbers are stored in our minds, and they don't need protection like gold, diamonds or cars do.
So a credit card or a bank account is...what?
A credit card is a means of debt ownership management. A bank account also.