I am wondering if resellers like these are part of the reason kodak made this decision..
I'm based in the US, so in a sense it's easy for me to do this.
Right now I have some amount of all 4 Vision stocks(50D, 250D, 200T, 500T) out in the freezer, along with some Mercury Marnau. I actually have two rolls of that-I'd bought a 50ft roll back in the fall, then bought 100ft this week when I saw it back in stock.
In addition to this, I have 1 1/2 rolls of Rollei 400 Pro that I bought in 2019 from a seller in Poland from the last batch of this made, 4x 100ft rolls of Plus-X Aero out of India(the current stock on Ebay seems fine-there are several threads here about it, and I've shot ~30ft of it), a 100ft roll of Portra 160NC, one of Kodak VPS, and a few other odd emulsions here and there. I've mostly been shooting these in a couple of Hasselblad A70 backs, but just yesterday I had a box arrive from Mercury that contained a 70mm insert for my Pentax 645N.
In any case, most of my 70mm gear, both film and supplies, is a mix of various Ebay sources(for most of the older films) and a whole lot from Mercury.
I've chatted with Zach from Mercury a decent bit, and he has indicated that he is fully transparent about what he's doing and remains on good terms with Kodak.
He has stated here, on Facebook, and I think a few other venues that ongoing availability of 65mm stock at least through him/Mercury is not a concern. The only stock that's a potentially in jeopardy is 200T, and that's related to whether or not Kodak makes more of it, not any restriction on selling it. The roll I have from Mercury was made in 2016, and Zach has said that this was the last run of 200T(or at least in 65mm). He's down to just a little bit and is only selling it in packages.
I'm not sure where other sources like Film Photography Project stand on future availability. For what it's worth, I did buy 2x 50ft rolls of 50D from them a while back. They will save you ~$40 on a 50ft roll compared to buying from Mercury(the math shifts a bit if you buy 100ft, as you're looking at ~$220 from FPP and $260 from Mercury for that amount). With that said, Mercury spools their 65mm on custom bulk rolls that are modeled after Kodak 70mm rolls, where FPP sells it rolled on a core. 65mm from Mercury comes ready to drop in a Watson or Mercury bulk loader, where FPP will need a bit more creativity and gets a bit unwieldy once you untape the rolll. It's manageable, but just something to think about. I've found so little use for 50D that I've lived with it-I'll continue buying 250D and 500T from Mercury as I need them.
Just as a bit of math too on 65mm, if one wants to shoot Vision films in medium format, the only other source I know is Cinestill. Cinestill charges $13.99-16.99 for the various Vision emulsions, and I consider their product technically inferior since it lacks the Remjet anti-halation later.
Mercury recommends 13ft of 65mm film in a cartridge, and I've found that this gets me 60-65 exposures in a Hasselblad A70 back. We'll call it 60, since that's exactly 5 times what is possible on a 120 roll in a Hasselblad A12 back. A 50ft roll of film from Mercury is $159, which is good for 3 full 13 ft. rolls with quite a bit left over. That's equivalent to 15 rolls of 120, or really more like 19 rolls. That works out to ~$8.50 per equivalent amout of 120. Jump up to a $259 100ft roll from Mercury and you get 38 rolls of 120(really 38 1/2). That makes it $6.84 per equivalent 120 roll. I don't think I've seen fresh 120 color that cheap since about 2010. The least expensive color offering I'm aware of is Gold 200, which before the price hike was around $9/roll, and as much as I love it as an inexpensive, reliable emulsion, it's a generation behind the Vision films. The current Portra films, if I'm not mistaken, are based on the Vision3 technology, but I think the last of those I bought back in December were like $60-70 for a 5-roll box.
