Execpt that's not how it works, you also have to factor in bug testing,
the fact that there is more than 3 people working on an rerelease, the Skyward Sword HD credits had 37 people across programming, graphical redraws, and everything else involved in in the portjob (a native one btw), not counting the credits preserved from the original and the 3 project managers from the team brought on. If they all were paid 100k a year (which definitely isn't the case), across a year at minimum to ensure it isn't a buggy mess, to make sure it runs well enough for the hardware they're targeting, and to make sure the new textures don't look wrong or need another redraw.
This does not take 6 months. This is something that takes multiple years. Even if we assumed that it took 3 years at most, that is still $11,100,000 (or $12M if we count the three project managers) at minimum, and that's off the assumption that every dev and artist involved's salery was 100k a year.
We also do not know the saleries of everyone involved. The main programmers could have had a salery of 200k a year or even 250k a year and the support programmers (both the explicitly listed support programmers and the ones credited for helping with the dev tools) 125k or or more. The Artists could have been paid 125k a month or more depending on what they were assigned to (such as the UI design and art, the additional Art made for the port, the actual redrawn graphics themselves), on top of marketing and advertising (which is generally agreed to be double the budget for making the thing its advertised.) PLUS the physical card printing (which has been known to cost upwards of 60% more than a 50GB PS4 disc for 32GB Switch Carts because there is more that goes into making one only designed for the Switch (and now Switch 2) than a Disc) which also takes from the profits because they still need to pay Micronix to keep making switch carts at all, even with the 8GB carts they would use for SSHD to make them since they don't make and suddenly that generous $12M balloons up by tens of millions of dollars, which eats at that profit margins
And don't even get me started on the Link's Awakening remake because it is a remake, literally everything that wasn't from the original like the level design or the items that was in it was overhauled from the change from sprites to full 3d models to the UI to even the music which required an entire team consisting of more than 3 people,
which is evident in the credits, where besides the lipservice given to the original LA's teams, consisted of people who did not work on the original LA, and of a far bigger amount than those original teams. Even if we ALSO assumed every single person involved in actually making the game (so no localization, counting 65 across that, the special thanks, and obviously the based on the old dev's work bit out of 244 credits and the 28 uncredited people involved with the music) was paid 100k a year across 3 years, that leads out at $62,100,000. Then factor in the above marketing and cart producton costs Micronix gets for making the carts, and the fact said profit doesn't entirely go to Nintendo's coffers with the Link's Awakening and Skyward Sword HD with some of that money going to Grezzo and Tantalus respectively and suddenly those $240M and $360M profit arn't as impressive, possibly even more so if you consiter the more realistic salieries of everyone actually involved in making both of them.
The Twilight Princess decomp on the other hand was open source and allowed anyone to contribute for free over its 5 YEAR lifespan, and the port is also open source PLUS doesn't offer anything unique that ports made from decomps don't already offer by nature of having the decompiled code availible besides maybe the native menus related to the decomp itself and the logo, the fact that because the decomp/port requires the original assets to be usable, they don't even have to do anything that isn't on a code level and the port comming for Windows first, so already the financial burden is significantly lowered by an infientesimal amount.
You already answered your query here. Zelda is a popular brand that attracts the eyes of millions across the globe, plus the eyes that are caught by any advertising for the games and anyone who picks said games off a shelf and wants to see what it's about. The games themselves are targeted at a wide demographic and designed with the idea that many, many people will play the game and has to be designed around the fact that anyone and everyone with a different skill level or taste.
This is not the case with mods, ROM Hacks, decomps, or even fan games because the audience they attract is comparitively concentrated as they attract people who are already familiar enough with the game (or the franchise or game formula for fan games) to be able to pick up and play them easily enough that the people behind them can immediately design them with that in mind. Consistantly popular mods like the Create mod for Minecraft was created and designed around people who spend many hours in Minecraft creating giant and impressive looking structures. Kaizo ROM Hacks are designed arround Speedrunners and the insane knowlege of the game they have of it while anyone who is less dedicated like most casual gamers get repeled off the first challenge presented.
You can't do something like a Kaizo hack when officially working on a major IP like Mario or Zelda unless you explicitly design the game arround it being harder than the difficulty traditonally experienced on a casual playthrough like ala Mega Man & Bass or even New Super Luigi U or you risk loosing players because they have a harder time playing it if they are not good at it, nor could you really have a mechanic change or additions that can be put into a rerelease without it alienating people like how Majora's Mask 3D's Zora Swimming changes put a lot of people who were familiar with the original off because of it working too different than they were used to.
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