Why buy when you can build? There are many places online that sell plans if you need them. I am building my own LWB delta cargo trike, and have it to the point where I'm using it daily. I'm thinking the $300 I have in parts (never mind the labor!) is a far cry from what is being charged for similar models if you can find them.
Please bear in mind this was at the rolling chassis stage, but it gives you an idea of what I'm doing. Paint will have to wait until spring, when the weather will co-operate.
I'll get a pic of it's current look and post it later.