About $1100.

A biscuit joiner is a circular saw. It cuts a short, crescent-shaped slot into which a thin, flat, oval shaped beech wood spline called a biscuit is inserted. Allegedly the glue soaks into the biscuit and expands it in the slot, but...jury's out. This can help align panel glue-ups and other joinery, but don't add much strength compared to a simple glued joint. Biscuit joinery was invented in the mid-50's, initially as a system for joining manufactured sheet stock like chip board or plywood. The patents have expired by now allowing anyone from Bauer to DeWalt to manufacture biscuit joiners. They're fine for attaching face frames or for aligning tabletop panels where the glue is going to be plenty strong enough, but they aren't appropriate for proper load bearing joints like attaching table legs to aprons or holding chairs together.

The Festool Domino joiner is a router. Using a straight up-cut spiral bit, it quickly routs out a small flat-bottomed mortise with rounded ends, which could mate with a traditional tenon but it's truly intended to make two matching mortises which will be joined by a loose tenon. Festool sells ready-made loose tenons called dominos sized to fit the tenons mortises made by the tool. A so-called domino joint is as strong or stronger than a dowel joint, in some cases approaching the strength of a traditional mortise and tenon, making it suitable for structural and load-bearing joinery. Floating tenon joints are ancient technology (examples dating back to the neolithic have been found) but Festool's contraption allows you to make them at the speed of a biscuit joiner. Festool introduced the domino joiner in 2005, and is still under patent for a few more years yet, so they're only available from Festool at frankly exorbitant prices. But I'm sure the likes of Ryobi and Stanley Black & Decker have them already drawn up and ready for production the moment that patent expires.