The point of 'spam' transactions... isn't the spending of money. The spending of money is just a work-around to spamming/storing arbitrary data on the blockchain.

That data, disguised in code or datafields like op_return, only serves a secondary purpose usually associated with memecoins, nfts or highly-speculative "crypto" etc.

For example a transaction like this

Is not about an entity spending 563 sats / 67 cents over and over hundreds of times... there's little 'economic' reason to do that.

Instead, this user is 'pretending' that the "pi" token exists, and an external database is tracking the "existence" of that token and "movement" of that token by associating it with certain outputs.

"Pretending" that those outputs, in an external database, represent the "pi-token" and therefore can be traded is the heart and soul of the spam issue.

The creators of such transactions pay fees just like anyone else, that's not in doubt. However they pay the fees to use Bitcoin as an arbitrary database... to do their crypto trading. They're not using Bitcoin itself as a monetary network or Bitcoin the asset in and of itself.

Attempts to 'filter' the spam by filtering op_return completely... have been unsuccessful since only a small number of nodes have to successfully relay the spam-like transactions to miners.

In this case, it's not op_return but a small amount of information "hidden" in the witness which is indicating the external existence of a token. The information is minor... but degens treat that information as a 'cue' to the existence of tokens and exchanges (especially those base in China/Asia) "create" the tokens resulting in a large amount of spam-like on-chain activity.