There are a number of facilities that do it. Before selling my boat this spring, I considered storing the boat on the Erie canal in Brewerton. My recollection was near $7K. That was including out and back in for 50' LOA. They offered a range of options at what seemed reasonably competitive prices. Was considering some upholstery work and an overall wax in the spring.
A takeaway that gave me pause was no power to the boat. On the Erie canal, you'll be in the building from October till maybe the beginning of May. Depending on your battery chemistry, that could be a long time. To be fair, if you wanted to come by and charge the batteries, that's fine. Just no power connected to the boat when your not there. Not all locations have that rule, so check.
Ted