While I most certainly understand your problems with such a thing, especially given the recent digital releases, I feel this is also a sentiment that will be shared by some others as well. Very understandable, given the sheer number of re-releases that Sayonara has been getting in the past few years. In fact, I'd normally be more inclined to think the same thing myself and I entirely respect it.
Realistically, there's no reason for anyone to get it. Sayonara is already available on 3DS, PC, and Vita. We're not even counting the VR release and the upcoming Switch trilogy, and this just sounds like it'll be a physical bare bones release. So, I'd estimate at around 29.99 - 39.99 USD for the purchase price (if they plan on operating similar to
LimitedRunGames). When you think about all of that, digital is easily the way to go. It's far more appealing, and significantly cheaper. Especially if you can get Sayonara on a Steam sale? Goodness! Heck, the whole trilogy on sale is a steal. but there's always that appeal of having a physical release, and that's what makes this enticing. It's also why I brought this up, which is something you had addressed as well.
Cost. and this is actually really interesting to get into.
You had mentioned the cheapening cost of Sayonara, but we've definitely been checking out different places as the title has more than retained its value if you're looking to get the game in the West. Importing a physical copy of Sayonara on the Vita, based upon the places I've checked that ship westward with no middle men fees, the prices are virtually identical if not more than what I'm estimating the game to be sold at. Ebay doesn't list the game any cheaper than 29.95 USD for a used complete copy. Play-Asia is asking for ever more than that. SolarisJapan is easily the most ideal, with a brand new copy, but that's still 29.97 so you could easily wait for the price to be released for this limited one and compare.
You can go through other places like Amazon.co.jp, Yahoo Auction, etc, but the further you venture outside the normal path to cheaper listings the more likely you're needing to go through a middle man. So say if I was looking to buy Sayonara for the first time, I'd have to use my Japanese contact to get the game cheaper through other means that are not normally accessible for shipping outside of Japan. For example, there's two listings I found on a usual go-to spot I use that cost roughly the same (19, 20 USD). By the time the shipping fee is adding and the handling by my contact, I'm going to be spending roughly the same I would getting it on Ebay for that price range. In my humble opinion, that makes this upcoming physical release compete quite nicely with the current priced versions of Sayonara on the Vita. That might not be your case with where you live, or where someone else might, and there's also cheaper auctions that can go up. However, this is what's available as of this moment and for those of us that have to go through those means this is a really wonderful thing.
Regardless of any personal thoughts on the worth, I genuinely believe this is really a fascinating moment for those that enjoy Umihara Kawase as releases thus far have only been limited to digital copies in the West. This could potentially be used as a gauge for companies to see how well this sells for potentially more physical releases down the road. Grandia was picked up by Sony only after they saw how well the Lunar series did, and that was all thanks to Working Designs taking a chance.
Is that a likely scenario? Probably not, but it still is a rather big moment for any Umi-chan fan. At the very least, it'll make headlines in various gaming blogs and outlets which will then further draw attention to the series once again. That's always a plus.
Is it worth purchasing? That's all personal, but I think it's worth bringing up because this will highly likely be picked up by scalpers and resold at incredibly inflated prices. That, would truly be a shame as any collector knows just how expensive it is to collect Umihara Kawase merchandise and games as it is.