We have 2 8.5 X 20 enclosed trailers. The oldest being a 2010 that had the spray in bed liner done when it was built for around $1000. When we had the new trailer built last fall they were quoting between $2000 and $3000 for it. I said no thanks and we used the roll on bed liner from the local auto parts store for around $400 in material and one days labor. We did the entire floor and 2 foot up the walls, no ramp as that is aluminum tread plate.
The original has held up well with the exception of the very back had a few pieces break off. We just cut a strait line across the back and then repainted that section. In the pictures the older one is the tan floor and does have a few areas that are discolored but the material is still in good shape.
For the new trailer it seems to be holding up just fine for the 2nd month of use.
That is the black colored liner in the pics.