I think a subscription area would exclude people who are vital members of the community who don't have a lot of spare cash. I'm sure there are long-time members who donate when they can, but aren't always able. (At the moment, even $25 would be a major investment for me, so maybe I'm just feeling a little hyper-sensitive.)
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(And on the OTHER other hand, I really like the idea of giveaways and the like to encourage more people to donate as needed. Even when I don't have cash, I'd be more than happy to donate a piece of art or something for a giveaway/raffle kind of thing. Don't know what the legalities there would be, though.)
From my long lifetime of observations

it wouldn't matter if it were 10 cents or 10,000 dollars, ALWAYS there are those who can't afford something and those who can afford anything. I'm self employed and a pretty thin string alternates with WOW what a great month, but every day there are financial choices
where I choose the priority. Some days it might be a $2.00 latte, others it might be $2.00 in the poor box.
I brought the idea up with hesitation because I'm not familiar enough with pagan interests and forums to know what people would be willing to pay for. I've walked a solitary path for a long time, Perhaps nothing? Perhaps the 2.00 donation a month is just right? Also is there other pagan forums on the web so the general member base is widely diluted? With the AT Tarot forum it is the biggest busiest on the web, and routinely has 700-1000 members on it at any one time. But a lot of what they have there for was added over a period of years.
In their monthly give away thread which is subscriber only, includes a full subscription, it also includes subscriber donations like padded tarot cases, personally printed decks, and books. The cost of mailing them is borne by the member who donates them. So the question would be if a give away that only includes those members who have donated their $2.00 for the month would increase those donations by enough to let the forum fly free? What do members here make or have someone else would think worth entering for?