If we are talking "clones" or at least using production models to think about here's my $2 worth (inflation!).
The Sony SS AR-1 could have used the Be tweeter, which is a drop in replacement electrically, but for $20 large they felt it was too expensive. Retail to driver cost: 20:1
The Wilson Sabrina is another possible model for using off-the-shelf parts. Retail to driver cost: 27:1 or more.
Wilson used the Vifa D27 which is pretty rough at the top end. Overall Wilson is balancing cost with output. That is, he's matching the $$$ spent with how much output each driver will put out, so in this case most of the driver $$ is in the woofer, and goes down to the tweeter which is a Vifa D27. $30 off the shelf. I don't buy the claims of custom work doing much there. Not a terrible tweeter but personally in the same price point I'd have gone with the DX25 or XT25.
In the middle range I really want to give the low-end Be tweets a try around $280. Of course if money is no object and you want amazing linearity and frequency response, the Mundorf AMTs are very difficult to beat and run around the same as the top end Be tweeters.
I guess my point is, I think the Sabrina is a good example (in terms of design) of a large floor-standing 3-way, but if I was building it I'd have to seriously consider the tweeter. Of course, nowhere in my head can I justify spending that kind of money, nor would I design such a big bass bump. Also, for $16K they still use the cheapest possible floor mounting spikes? Give me a freaking break.
Best,
Erik