Just checked the MD DMV website. I don't see where they offer permanent plates, but maybe I'm looking in the wrong place.
Trailer registration fees in MD are also based on weight. Since my old trailer and current trailer are less than 3,000 pounds empty, they'd be registered at the lowest price per year.
So yes, if you have a monstrously big and heavy trailer, you're going to pay more per year than those of us with smaller ones.
Everybody has to decide on their own which laws they can scoff at and still sleep at night. I tend to be a goody two-shoes when it comes to following the law, because I don't want to be fined heavily or go to jail. I have a fear of being confined without the freedom to come and go as I please.