It's not going to be cheaper on disc elsewhere when it's OOP in North America (US). I don't believe the NA distributor has replenished it's original pressed stock and who knows how limited that was to begin with. The digital price in the US has been $39.99 for a couple of months which is a lot better than the original $59.99 that probably scared a lot of people away.
From what I can tell the online retailers that even have a listing for this game are still using the original $59.99 USD SRP and most don't even have it in stock. It's OOS at Bestbuy, Amazon and Gamestop. Target and Walmart don't even have listings for this game. Depending on the state you live in you might not even be able to walk into a Gamestop or Bestbuy even if they had it in one of their stores.
It didn't help the North American market that the NA distributor held back it's digital and physical release for the game until January 7, 2020 while the European release was November 15, 2019 by a different distributor. Microsoft also pulled the digital release from Coming Soon and it kept getting pushed off the Recent Games page in the US Xbox region because they were still using the original November release date. Even if you found it in those categories or did a manual search you couldn't even purchase or pre-order it digitally if you didn't do so before the release date got pushed back.
How many sales did they lose out on due to this issue and by releasing it after the holidays? How many people don't even know this game exists? There was minimal to no marketing. Sometimes you 'll see an ad for it in the MS Rewards App on the console but that isn't much.
Did the negative reception to Dark Fate hurt this game? How many people ignored this game because the last several films were not as good as the original 2. How many people figured this game was an adaption to Dark Fate? I actually liked Dark Fate but fully understand why people didn't and why they may have chosen to skip that film altogether.
Then you have the people weary due to the developer's past Rambo game and that they were a smaller studio and there wasn't any apparent involvement by Arnold or anyone else from the films.
If they could have had a game trailer show during the previews before Dark Fate in at least some of the larget markets. Granted, that was probably beyond their budget.
Barely anyone knows this game exists. I have heard nothing but good things from people that have played this game. Still, $39.99 is a bit much for me and given the recent EU PSN digital sale I think I would rather wait for a $20-$30 price point digitally. I wouldn't be surprised if the game showed up in Gamepass in the next year or two either.
/rant