That’s a valid point. But…

“However the amount of money that dedicated spammers can earn from spamming the network is almost always more than what a user in a less developed country can pay to take part in the same network. And sometimes a user in a more developed country too.”

That’s a pessimistic assumption.

- PoW needs not to be ever increasing, this is not a blockchain

- the point of PoW/MP(micropayments) is not to eliminate spam altogether, there will always be a point of diminishing returns to increasing prices/difficulty

- maybe it’s worth to define what exactly we mean by spam: is it the flood of undesirable content? As seen on early bitchat geohashes? Is that annoying person begging for money once on random posts? Should we consider synthetic FUD funded by some sort of elite as spam? Etc

- PoW/MP is a viable way to, at the very least, rate-limit spammers in such permissionless/p2p/distributed systems, but it can’t stand alone

- ultimately we (IT) have come to the conclusion that security should be implemented in layers because annoying the attacker until either he gives up or some alarm rings is better than investing in one giant “impenetrable” layer. So there’s no shame in combining WoT with some sort of bootstrap list along PoW and common sense

Now it’s my personal opinion that MP is better than PoW, not only because it removes friction from end user’s devices but also because it can be an effective way to fund infrastructure. In this case, a wave of flood spam could turn into funding to develop better spam protections 🤣

But still, I think you’re right to think about the impact of well funded bad actors, though I don’t think they are usually called spammers.