I've got several U-Dump and Triple Crown trailers here. Helps that both are local. U-Dump has a turf trailer that I own - turf tires and runs on your tractor hydraulics. Only down side to this trailer is the bottom floor is exactly 48" wide, so it's tight when loading pallets of sod. This unit cost me around $3,000 (no delivery charges) when we bought it 10 years ago.
I also had U-Dump custom build a normal 6' x 10' dump trailer with 10,000# axles, two 12,000# lift cylinders, a 3/8" steel floor and 18" sides. I had them install the battery mount electric/hydraulic pump and then we plumbed it to also run using tractor hydraulics. This way you have both options depending on what's towing it. I over engineered this because I know my guys will overload it when hauling dirt and rocks. This unit cost me $4,500 (no delivery charges) when we bought it 6 years ago.
If you have one built, I highly recommend getting two lift cylinders. A single cylinder will tend to twist and bend when lifting a heavy load.
I'd also spend the $20 and put a solar charger on it if you are getting the electric option. You can get these from Northern Tool. We buy the two packs for $30. Just enough trickle to keep them charged and ready to go.
http://www.udumptrailers.com/