I think there's a lot of honesty and practicality in your response but not the transparency or clarity needed for this to scale. These networks require buy-in / critical mass to function as intended, and not knowing if I (or my friends) will agree to the pricing terms after I get my network on board is a hard stop for me.
I do like the idea. Well designed limitations can add a lot of appeal, and in social spaces especially they can be fun to play within.
The two that I used to maintain personal connections and communicate in ways worth archiving were Myspace and Facebook. For Myspace I was a teen. Same with Facebook. My connections were from school so if either disappeared I'd just have to talk to them the next day. Also both had attained critical mass at some sort of scale by the time they popped up on my radar, and were fairly new ideas so it's not like I was able to shop around. I just went where my friends were.
I do like the idea. Well designed limitations can add a lot of appeal, and in social spaces especially they can be fun to play within.