The "fees are the filter" argument for regulating spam only works when the fee is charged by the party providing the service to the party receiving the service.
That's how consensual transactions work.
It would be the spammer paying the node runner to store his arbitrary data.
What we have is a third party paying a fee to a miner at the expense of the node runner who is on the hook to store the data, for free, FOREVER.
That's parasitism. Rent-seeking.
This is an example of Bastiat's That Which is Seen, and That Which is Not Seen.
In the broken window fallacy a broken window is viewed as good because it stimulates economy by providing work for the window maker. The more windows you break the greater the benefit in stimulus.
But what is unseen is the damage done to the property owner's disposable income, such as a new pair of shoes that he can no longer afford. He has been deprived of the benefit of his wages, and furthermore, so has the shoemaker been deprived of employment.
Spam is a broken window.
The spammer enriches himself, and shares a portion with the miner. The sender of the financial transaction gets stuck with higher fees, and the node runner gets stuck storing the images at his risk and own expense for the benefit of the son of a bitch that broke his window.