Joining is free -- it's free to post recipes, but when you post those recipes, they are public.
If you're looking for private-only recipes, that's a feature request, and, as written above, it'll likely be through a paid subscription offering that is not yet available. We definitely don't think you should have to pay for a product that you do not find useful. That's why we not only have a 30-day free trial, we also have a No Questions Asked Money Back Guarantee that you can take advantage of if you'd like. Simply return the product within 30 days of purchase and we'll fully refund your money, including any taxes.
The private-publishing feature does require server space, and ad revenues cannot offset that (since the recipes are limited for view to just a single individual); while we offer many, many things at low prices, it's very unlikely we'll be offering this of charge.