a extra 50 bucks max. those sheets are run by the millions of feet at a run. 1 extra clear coat spread across the run of any given color pennies.
heck I would be happy if they just went back to the quality of panels just 10yrs ago
Well probably more than $50 bucks. If you consider that they use a very inexpensive industrial single stage topcoat as it is right now.(which is why it chalks so fast, UV screeners are one of the most expensive components of the raw materials in paint) Adding clear would change the color to a base, then they have to bake that to make it dry productively in the manufacturing process, then clear the panels, again bake it to speed the drying process. The cost of the product is more per ounce, and the extra manufacturing process would add enough cost that people might not want to spend the extra money. It would open up a lot of new color options with base/clear, but again slow down the manufacturing process which will add cost.
To the original question- buffing it and keeping it protected it is the only way to keep it looking nice. Remember the film thickness on these things is very low, probably around 2 mils dry film thickness, possibly less, so stay off of the rivets as much as possible. If you are going to buff a black trailer use the finest compound you can get away away with, and a foam compounding pad running the buffer around 1500-1800 rpm's. If your rpm's are too fast you will just dry out the compound and it won't be doing you any good. Keep the buffer flat, don't use the edge of the pad, and then slow the buffer down a little more, and hit it again with a black(soft) foam pad with a machine glaze to remove the compound swirl marks never buffing it all the way dry, and finish it with a 3M product called Ultrafina with their blue pad. It's full of mineral oil, but will make your black trailer look nice. Never buff it dry, wipe it off with a microfiber cloth. Then it's time for a protective wax. I like to put that on with a DA or a random orbital polisher. Again hand wipe off. Piece of cake right.
Like someone else said, with a white trailer the process is a lot simpler.