I was looking around for the 700x40 Marathon Supreme and everyone I checked (beyond domestic suppliers at $75 each) longer carries them. The more I looked, the harder Supremes in general were hard to find. I'm looking specifically at vendors in EU that had good prices on them(half of domestic). Looking at the Schwalbe website, they are all but tapped out too. I started by sending emails to various EU vendors asking about supply and they replied they no longer carry them. I finally sent an inquiry to Schwalbe and received the following reply:
Thanks for your e-mail. Marathon Supreme is being discontinued with its direct replacement being the Marathon Efficiency which you can check out in the link below. It’s based off the same casing and protection belt, has a smooth center line but is a bit more versatile with it’s cornering tread texture. We make it in the 700x38c (40-622) but we do not offer it in 26” anymore.
https://www.schwalbetires.com/Marathon-Efficiency-11654366
Not sure the Efficiency is a drop in replacement for the Supreme(a little heavier, though they seem to be very conscious of preserving superior rolling resistance)..I suspect the Supreme is a causality of the e-bike market, to some extent. Very sad turn of events.
The good news, for me at least, is I was able to stock up on 2 sets of 26x2 last fall and 4 sets of 700x35 just before the end of the year when they seemed to be getting harder to find. Why so many?..it's my favorite road tire and I have arguably too many bikes(between my GF and myself) to mount them on.
I know some folks here are partial to Supremes...