While the "never" wasn't correct, they certainly hardly ever do. And the 3ds wasn't sold at a loss its whole life, let alone the 3ds XL, 2ds, New 3ds, or the New 3ds XL. Even for the one that was originally discounted, parts get cheaper to make overtime, especially at the rate they were making them after the discounted $80. The 3ds absolutely was a massive profit for Nintendo down the road.
The GameCube, while selling horribly and at one point at a really low price point, actually DID get them profits due to some smart business decisions on their part:
-Offloading development of less popular IPs to Third party studios reduced losses.
-Started publishing Mature games (like Eternal Darkness), and started making profits off those.
-The GameCube didn't break hardly, so they had reduced expenses fixing ones sent in to them.
-No DVD player capabilities helped reduce cost of making the system.
-Received a lot more multiplatform 3rd party games than the N64 did because of how powerful the GameCube was. They get a cut of each of these sold.
-GB adaptor encouraged more GBA software sales (profits) so people could play them on the "big screen." I absolutely loved this feature, in particular! Playing Pokemon Gen 1-3 on my TV was glorious and blew my mind haha.