WP Send does not include any pricing or membership features. However, the plugin works with all membership plugins out there.
If you have a membership plugin installed and you have different pages assigned to different pricing plans, you can add the shortcode with different parameters.
For example, you could have 3 pricing plans, Free, Advanced and Pro.
You will have 3 pages, each assigned to a membership/pricing plan, and each of these pages will have a different shortcode:
[send limit="32" expire="3"]
This is the Free page, with a limit of 32MB and 3 day expiration.
[send limit="128" expire="7"]
This is the Advanced page, with a limit of 128MB and one week expiration.
[send limit="1024" expire="30"]
And finally, this is the Pro page, with a limit of 1GB and one month expiration.