it was said in jest about double the shaves, but that is how you use a shavette, it's a cut throat that takes a disposable blade, you snap the blade in half (very easy to do, leave it in the packet and fold down the middle) fit it in the hilt and lock it in place. (you seem to know shaving so I guess you know this already) yes I'm aware you can get single edge blades, but they tend to cost more, also aware you can get shavette double edge blades, see my point below about shops.
I don't really care if wilkinsons aren't seen as fashionable, I've used most of the others and still find them more than up to the job and I can pick them up in the shop without having to order online or visit a specialist. I did like feathers but didn't get on with astras or derby. have about 400 supermax to get rid of as well, they blunt in 1-2 shaves and aren't that sharp to start with, others rave about them though.
I do have a double edge, funny enough it's a wilkinson sword from 1970 something, clam shell opening all stainless and very nice to use, but I still prefer the shavette (currently using a parker 31r, it's lasting well in comparision to the plastic scaled stuff).
as to 100 shaves to a blade, I assume they are 12 years old and not actually shaving anything off.
I haven't used a multiblade in 10 years, I have an electrical phillips for when traveling as I tend to go hand luggage and you get funny looks with a cut throat. it's hard to believe that there are forums devoted to shaving these days, 10-15 years ago you were looked at funny for even suggesting using anything but a multi blade, now it's a fashion item to have DE, oh how the world changes I guess.
happy shaving.