Actually, I think it would be cheaper than going all the way to the moon despite needing the same high exit velocity.

A moon-orbit shot would require the supply ship to carry its own moon-orbit-insertion deceleration reaction mass at take-off, whereas no such thing is required when we're "handing over the hamburger on the highway" both going in the same direction at the same speed.

Which, incidentally, is not such a big deal as you're making it out to be - they do technically similar problematic rendez-vous in orbit all the time, albeit at lower speed.

The great thing about not carrying deceleration reaction mass all the way up is that the same amount of propulsion gets you much more load capacity as all fuel/extra-stage engines you don't take along can be replaced by useful cargo mass. Or you need _exponentially_ less takeoff fuel if you simply take up the same cargo mass, and leave the deceleration mass/engine stage out.