Omg. It's so simple. Hyperspheres are way too thick anyway. Most of you are all silencing standard stems. Not longer ones like in the hhkb type s..
So.
You are losing so much travel.
Every now and then I see a few photo albums of people buying hole punches and punching out their own rings. I've been doing this from the start with 0.25mm silicone sheet. The difference is incredible and no noticeable upstroke is lost.
Do not support hypersphere.
So before I start, I have to say I bought 2 sets from him before and there are no regrets. It worked out well for what's intended, that being said there are still a few minor drawbacks.
First like Fullcream said, it's still too thick. You do notice the travel reduction.
BUT it's also the thinnest rings that you can buy (without making it yourself). So in this sense yes he did corner the market since there are no other options as thin as this.
That being said this works a little bit better on Realforce and NovaTouch (since they have taller keycaps so it mask the reduction in travel a bit), and on FC660C and HHKB it's more noticeable that the travel gets reduced (shorter keycaps).
As for pricing, it's actually been discussed before, the main reasons why the cost they are are:
1. Research, as some people pointed out he put in his time and effort to test the materials.
2. Order quantity, since he's only 1 person he's not a multi-million dollar company like Razer so he can't order them in the bulk amount that would lower the price low enough to make the price per unit super cheap.
3. He has tried to contact massdrop before regarding acquiring a larger order but I forgot why he said that didn't work out (maybe massdrop want to take a bigger cut).
4. Also how it's build, like people mentioned he layered 2-3 types of different material then had them stamp out the shape. I think this is a bit more expensive to make than just rubber o-ring.So while yes it cost quite a bit for what it is, but it still is the cheaper/thinnest options available.
Hopefully one day someone will sell the pre-cut 0.25mm silicon rings then I'll definitely give that a shot.