Manhattan Mini Storage does free trips to/from your storage unit, you just have to book in advance and fit into a van. It was awesome when I was using them.
Also, from MMS regarding the van: Keep in mind that the Storage Taxi provides a one-way trip, not a round-trip. For example, if you need to bring more items into storage, you would book the storage taxi to help you get the stuff there; getting home, though, you'd have to rely on the subway, a cab, your bicycle, or your own two legs to carry you.
This is sucky.
Another place I looked at did storage by the cubic foot, so you'd never see the stuff in storage (and they could presumably save money by packing it better). Seems like that would be a great model for you to use for people who never actually go to their unit.