That is what I want to emulate, all like it seem to have walls on the platform, I want mine to be smooth to the edge so I have a larger flat space. Plus 1k is a pretty steep price.
Not sure what you're wanting to do. You can't make the slide out part wider than the wheel wells - so to me it makes sense to have 'edges' to the platform to keep stuff in place. I don't think $1k is bad considering what's involved, but sure you CAN make something yourself cheaper.
The idea mezmochill referred to will work fine, you'd have an upright portion fastened to the ed with the bearings, and the 'tubes' will be fastened to the side of your platform. Don't have to do it drawer style.
I drew this design up a while ago for making drawer slides any length you want using the same principle as the bedslide. It uses cam follower bearings that ride in 2 pieces of C channel, one (inside) fixed to the bed, and one fixed to the drawer or paltform. If you fix it to the side of the platform it'll be lower profile than the bedlide type.