Since I’ve posted my answer I’ve tried to rerun some of my maths. I stand corrected.
I do maintain however that currently POS and Upwells have a price gap. Mostly going by start-up price, not by maintenance price.
A POS might not be cheaper, but you can reconfigure a POS to be a refinery for a week and a manufacturing base the next. With Upwells, it’s very much impossible because of their concept. One Upwell structure can only effectively provide services to one type of activity, no matter how much reconfiguration you try to shove in it.
For their price, a POS has greater modularity. An Upwell has on its side practical use.
The issues you describe with POS remind me of something.
Back in the days, POS meant whether you could effectively say that you owned the place or not.
They marked how much an alliance or corp could do to effectively defend their territory.
It allowed to establish more complex off-grid logistics like jump bridges, that allowed to gain advantage over possible invaders or intruders.
Now, Upwells take the place of POS. But you can anchor them essentially everywhere.
Honestly, if CCP just pushed to get rid of POS, we likely wouldn’t be having such a conversation. The topic would be “Cheaper Upwell Structures to help Small Corps”, rather than what it currently is.
As long as POS exist, there will always be the (justified) perception that POS are cheaper.