Comes down to 3 reasons, they're good quality, sort after for years and they're pretty much complete and stand alone out the box (e.g. not many of them have DLC, they're not yearly or frequent releases and so on)

this topic pops up again I see.

I think most have answered the question with good points.

Because they keep selling and nintendo games are the majority of the small library of the wiiu, a shame there are good ports like tekken tag 2 who are bargainbin levels meanwhile

Lasting quality I guess.

Iwata said in the past that he wants to uphold the perceived value... The games sell well so I don't see it as an unsuccessful strategy on his part. Normally when a product moves more copies it generally gives the maker more revenue due to exposure. I have to wonder if the psychology of it works the same way to someone who doesn't want to spend that much on a new game and if said person would want it more the longer they waited for a possible drop in price.

Supply vs demand

tagged

Want a better example? Just check the charts, you'll find Mario Kart Wii, still charting practically every single week despite being an 8 year old game on a previous gen console.

Really, Nintendo games are way less frontloaded than any other games, so there is no reason to slash the price in half after merely a few weeks to keep the momentum going, they just keep selling over the course of an entire generation, and some games even 2 generations when backwards compatible.

games are still relevant after years.
a smash bros title is fresh, relevant and lasts for a long time. Each title is made like it was the last, and it would be the definitive version that lasts forever. (until the next version, but only 6 years after)

also, the suply is kinda limited.
By offering not many more than demand, the prices keep high.

Is good for nintendo in revenue side and image, let the sensation that nintendo games are more valuable.
But the bad side is because the games would not be acessible to crowds of people. And even less people will know nintendo games in the long run.
The nintendo market is becaming a high valuable niche games.

I think what's strange is that third parties don't follow Nintendo's example.

I'll never buy a third party games on PC or console at full price because I know I'll be able to get it cheap at some point.

Nintendo games I buy day one because I know that'll be the price for awhile.

I think there are a number of third parties who'd make far more money from me if they never reduced their prices. I actually have the disposable income to spend on games if needed and I think they're worth it. Of course, with pc, if prices never went down it would probably encourage piracy.