I've always loathed the term "Nintendo Tax" because it implies some kind of penalty, like a wealth tax or a vice tax. Though I can't argue that it's not a real thing - Nintendo's best games hold their market value far better than rival games, even from other top-tier Japanese developers.
Still, I would approach this phenomena from the other direction. Nintendo is not able to maintain high prices because they're somehow fleecing people (as a tax would imply), but because they work to make games that stand the test of time. And then back it up with a sales strategy to match.
So much of the industry treats video games as ephemeral entertainment - something to consume, and then throw away as you move on to the next game. It's the traditional media model for TV and movies extended to interactive media. And for most of the industry it's an accurate observation: game sales are ridiculously front-loaded, and few games (especially single-player games) have a long tail. After the initial hype subsides, you need to lower your price quickly in order to keep unit sales (and thus revenue) from cratering. All the while you're already hard at work on next year's game.
But Nintendo has been able to channel the lifecycle of board games and card games. In their eyes they aren't creating media, they're creating a digital plaything. They're creating something that you'll play now, but you'll also want to play next month, next year, next decade. Case in point: Mario Kart 8 is 11 years old and the only thing that has really diminished its value (and sales) after all of this time is that it finally has a successor in Mario Kart World.
When is the last time you saw a permanent price cut on Monopoly? Uno? Settlers of Catan. The occasional sale, sure. But a copy of Catan is still going to sell for $40+, even today. That's the business strategy Nintendo is tapping into. If a game is good - like really, really good - and it's repeatedly replayable, then why does the price need to be cut soon after launch? Why can't people come along and discover it years later? Why does it need to be priced like it's a quickly depreciating asset - like a movie instead of a board game?
And that is the ultimately where the Nintendo Tax as we know it comes from. Make a game good enough, make a game gamey-enough, and don't devalue it by replacing it 3 years down the line - and it's something people will want to buy even years later.
Though this is a relatively recent phenomena. It's only after we hit the PS360U generation of hardware that systems had enough processing power and memory for games to not be constrained and do whatever they want. And that games stopped being obviously dated in terms of visual when compared to the previous generation. It's no coincidence that this was the last generation where Nintendo offered their Nintendo Selects line of discounted games.
