I decided to do a rapid development of a design for a Makerbot clone. This was done in less than 1.5 hours. It is a simple RepRap concept that has about 75% more build area than a MakerBot. It uses standard Misumi 20mm extrusions shown in white and the slide extrusion shown in gold.
The Y axis rails are used as part of the frame structure. I did not model any motors, but my thought was belts for X and Y and a leadscrew for Z. The total cost of all framing and slide extrusions is $55.53 using standard Misumi pricing (no discount) plus $1 per 100mm pricing for the slide extrusion. Misumi brackets, screws, nuts etc should cost less than $30. It requires 13 v wheels which should cost less than $10 in nylon (fine for reprap load) or about $60 for stailess steel double row v-groove wheels. No cutting, drilling or tapping of any parts on the frame or rails is required.
That puts a ready to go frame and rail system at less than $100. Compare that to $200 for the Makerbot laser cut chassis alone (no slides).
This is just a demonstration of the rapid development possible with this bearing idea, not a real design to be critiqued.
Edit: added a second image with motors.
"If you didn't build it, you will never own it."