Actually, I think it would make more sense if non-guild members got charged alot more for using it compared to guild members. Perhaps guild members of a certain rank(probably the second rank so they can "prove" they are actually part of the guild in more than name only) would have the price reduced by alot. It would make sense the mages guild would want people to give them money. I am sure this is easy to implement, but the inner workings of dialogue and such isnt something I know anything about.
That would make sense, absolutely, but that's not really what I was arguing against. It's always been all or none with services. The MCP adds the ability to filter specific services, and with MGE XE you can alter the GMSTs from within the game, which is what you would need to do to change the guild guide prices significantly for different people. Though you could do dialogue-based teleport (like the way you get to and from Mourhold, just add a fee) and just remove the travel services from the guild guides easily enough. Kinda makes me wonder why it's not been done, at least, publicly. Or that I know of.