And how do you get 2 three-ways and a single pole or 3 three-ways in a single gang box with one of those devices? Seems like box fill will be a problem.
If you think that's fun you should do the 2 gang versions. Called the double 3 desbard. Back in the 50's or 60's maybe they thought it was a good idea. No need for a 6 gang box when you can fit 6 switches in a 4x4x1.5 box with pipes comming in the sides. I don't know if box fill calcs changed over the years. All I know is when they did this the conductors would only reach outsid the box a 1/2 inch because they had to save space.
http://www.kyledesigns.com/category/11_home_decor.1_switchplates.width_despards/
Those switches are expensive and can be difficult to get. Such as (2) 3 ways, (1) SP, yoke, & trim would cost $55.00 to mail order at the place above, plus shipping. Basicly I think everything is all left over stock. It could be dirt cheap because the store wants to get rid of it, the price could be stuck the same as 25 years ago at an old hardware store, or it could be gold to the person sitting on them waiting for someone that needs one.
Another problem with these are the switches snap in a different direction than a standard toggle. Meaning sometimes a homeowner swapes one out and the switch is sideways.