WP Member is a premium membership plugin that offers unlimited membership and subscription levels. Content can be teased to visitors to encourage new subscriptions, and you can display an error message or redirect unauthorized visitors.
The plugin allows you to receive payment via PayPal or Google Checkout and it can be integrated with bbPress. You can also drip content to members over time. It allows you to protect all your content, including posts, pages and downloadable files.
Pricing: $47 ( One Year) | $97 (Multisite) | $147 (Lifetime )