I think his main point might be what Mattel paid to MLB, NBA, NASL, NHL, PBA, etc. to license their logos to include on the box. The sports games themselves would still have been great. Mattel sure did waste a ton of money on licenses.
Coleco did the very same by using licences to make most of their Colecovision games
That's also mainly why you don't see Plug n Play stuff of those consoles as much as you would see Atari2600 stuff