In the end, I think it should be a combination of things. A donate button should always be available to just straight up give, if it's a bit hidden. Have a small friendly reminder drive once a year to promote it too.

The barrier is a really nice idea, but it will certainly piss people off. Not that it's a bad thing. I think we have something unique and valuable here that it's a good consideration, and it discourages assholes, and it regulates the fluxes along with keeping the culture preserved. There were some good points raised on poorer countries having access limited then, but there's certainly ways around that. I haven't thought it through that thoroughly yet, but there are a number that pop into my head immediately.

And the more I think about it, the more I like the Conflict Tower approach as well. We already have a good number of meetups. Having one that happens to have a 'Members Only' meeting during it wouldn't be too bad. It's scalable too, and can be "filled" and finished if the site feels satisfied.