I have an established service/business I have been running for years, and I am considered an expert in my field. I am rebuilding our very old site, which will have many new features and a membership aspect. Unfortunately, my pricing has remained the same over the last several years, and I have always given away more for free than I should have from a business standpoint. I want to make this a viable business model and compensate myself for the time I pour into it. The new site launch brings so much to the table, but it will also cost more to maintain. How do I raise my prices without losing my customers? How do I price our new products without pricing them out? There is no one else who provides this local service.
High level, there are two ways you can go with this: Subscription model or payment for individual transactions/access to content. Subscription sounds like the best model here.
Judging from what you write, membership is a new thing for your site. So you should be free to price it as you want to. But remember, that whatever price level you are currently at, will serve as an anchor for your existing customers.
Also know, that no matter how much more you bring to the table, if you are too expensive, your current customers will look for alternatives. But it could be, that you are really better served by having a smaller volume of customers, if they just pay more.
My first step would be to understand on an individual basis, who your customers are, how they use your existing service, and how you think they will use your future service. Do phone interviews, surveys or something like that. If you are alone with this service, your customers should be loyal, and willing to offer their opinion to you. After that, you can decide on a viable business model.
Feel free to contact me, if you would like to discuss this further. I offer first call for free.
Good luck with the expansion!