I did some searching on the WordPress plugins page for a plugin that might work, and found a combination that may suit your exact needs (I have not tested these plugins, but the number of downloads of each tells me others have found them useful).

There are 3 plugins to this solution. A discount plugin, membership plugin, and finally WooCommerce to membership plugin that will connect everything together.

The first is the WooCommerce Discounts Plus plugin that allows you to do discounts in WooCommerce. Next, the s2Member plugin found on their website covers the membership aspect (looks like downloading the Framework option at the bottom of that page I linked should fit your needs). And finally
WooCommerce and WP eMember Integration will allow you to accept payment for a membership via WooCommerce.

Hope that points you in the right direction. Best of luck, and let us know if you need further guidance.