Client needs Ubercart member sign up function, but there is error with edit/option_prices I have a Drupal 7 client with Ubercart installed. They would like to add a Membership feature to their site where the members can receive a discount on their products and services. 

We have Ubercart Price Per Role installed (in spite of it not being updated since 2013 which makes me nervous), which has added a nice little Member Price field in Product. I have added a test Product Class called Memberships to allow for membership levels. 

I understand that a Role can be assigned to a Product Class through Attributes and Options to allow for membership expiration dates. Attributes and options have worked just fine for other products, but when I clicked the link for 'Note: "Price" column is the default option price. To set option prices per role use the options prices form.' 'I get The requested page "/?q=node/test/edit/option_prices" could not be found.'

Now it is entirely possible that I am trying to do it all wrong and that fixing that error won't get me the solution I'm looking for.   So, I would also like to hear hetherw I just headed down a rabbit hole, as well as finding out why the edit page cannot load.
If there is a problem it sounds like it's an issue with the menu tab links being generated for your nodes; node/test/edit/option_prices isn't a valid path, it should should be something like node/$nid/edit/option_prices.

The module enables that path if the UC Attributes module is enabled. It sounds like you've installed that module so I would substitute "test" with whatever product NID you're trying to test. Once you've confirmed it's working there, you can troubleshoot why your tab link is generating a bogus path.