I have a Bosch belt sander (75mm) that looks very similar to the Festool BS75. I can get a frame for the Bosch for floor sanding that is very much like the BS75's - but it's cost me $251. Then I'll have a old Bosch belt sander with a frame an no Systainer for it.
In operation it's probably as good as the Festool (remember, dust collection has technical limits with the mechanics of a belt sander).
I'm tempted to hang onto the Bosch regardless as it also has identical upside down feet to the Festool, so it can be used as a linisher.
I just looked on US Ebay and can see a Bosch belt sander identical to mine (mine is 240v).