That is about it, you pay to extend the community. Do you understand the difference between join and extend? We have an established community that welcomes newcomers to replace those leaving - that is joining. If you want to build a larger community, then great, go ahead but make sure you don't get me to subsidize your growth.
Why is it "your" growth and not "our" growth? As a matter of public policy we seem to have decided that "we" "need" to have growth, so I don't see why you feel that you're off the hook in this.
-k