He closes the portal. "I'm happy to help with transport, but it's slower than a normal teleport if I don't set it up in advance. I can open a portal a mile away every two or three seconds, so it takes me hours to get to the other side of the continent. If I knew in advance where you might need to go, or a few places, I could keep really small portals there that wouldn't cost me much and make a big one when you need it."
He's considered selling transportation services, it's the obvious thing to do with portals, but the main problem is that the portals rely on him and he can't really ask someone to build their business, let alone an industry or a national trade route, by relying on his personal availability, and if he did he'd be committing not to use his portals for something better down the road. What would be really great is opening permanent portals, and he thinks (or hopes) it should be possible, it's less of a modification of what his spell does than planar ones, but he's nowhere near there yet.
A few on-demand trips, though, that much he can do.