They are premium games quality-wise, but if someone gave me the best five NES games in a bundle, I wouldn't pay $60 for it, because over time the retail value of older games diminishes. In 2040 they aren't still going to charge you $60 for Odyssey, unless they totally remake it.
That said, I don't think the price of the collection is so ridiculous as to be indefensible, but its limited nature is upsetting and the fact that they didn't do much to go above and beyond for an anniversary collection other than upscale the games and provide some music is a bit underwhelming.
To be fair though, a bundle should be cheaper than the sum of its parts, and the Mario collection isn't (or at least, wouldn't be had they ever actually released Gamecube titles digitally), so I won't challenge those who say it's overpriced.