Are we talking livaboard...at the dock...or cruising?
Brian, first thing you mentioned is marina fees. Most of us out cruising spend little time at marinas. Less than 15 days per year is quite easy most of the time for most of us. Mostly.
15 days is one marina stop a month, or a tad over. That seems very low to me. How are you making your water last a month at a time? Watermaker? Seems there are a lot of places i would not run that. What about showers? You need hot water for showers. Generator or main? How are you keeping up with your power?
There are workarounds to these things. We have not been in a marina since The end of October. But we have also invested in the systems to make it work outside of one: generator, 780 watts solar, good tender, etc. I also prefer to keep a clean boat (wash it once a week or so), we prefer to shower aboard, etc. Others may not care about that stuff.
I am not here to tell anyone "this is how you should cruise". Instead, it is how we do it and make it work. I suspect that most of those in the 500 crowd will be in for some real surprises when reality kicks in, or they will be forced to live in a level of comfort most of us would not consider. I suspect that will lead to a very short cruise.
Understand, if I was taking a 6 month hiatus then i would just deal with a lot more lack of comfort. But we have been doing this a long, long time and the reason we have made it work (for us) was that we saw the boat as our home and we were determined to make our home comfortable to our level of standards. Others have a different level. But most of the folks which we have run across cruising on the cheap have generally had a very short timeline in which they would be on the boat and were willing to do without many creature comforts. We have no end, per se.
Another point about marinas, they allow you to run air conditioning. How are you going to get around ac unless you sail pretty far north for the summer? You have to be pretty hardcore down here to go without air conditioning in the summer. I suspect that Chesapeake south would be very, very uncomfortable. And while we could sail north, we actually prefer the keys in the summer so that is not an option for us right now. So the summer months land us in a marina full-time.