They are £5.99 at Screwfix. When other makers get on board, with single, FCUs. etc, expect them to drop substantially in price, as did screwless downlighters.
They are well overdue. They still do not eliminate Wagos at the back of backboxes for ease of 1st fix testing.
I do not know what max amps the connections on the back of these MK Rapids is. I assume 32A.
Some 4mm radials go over 32A. So best fit a ring in that case.
Nevertheless, a great advance. We are still about 40 years behind Denmark, Germany, etc, where screwless sockets are the norm.