They'd be reasonable regardless. There would still be the option to get everything for free.
But seeing as this game is a regular platformer that's looking to be one-and-done with a metric ton of content from the onset, I have a hard time seeing this get a DLC gameplay extension. Getting 106% will keep players busy for months, never mind the TFB relics.
Hell, the multiplayer modes are couch co-op and we don't know if those will even get online options.
If anything, one's gotta rather wait and see how On The Run's battle packs will work, since those seem to be the only things to purchase for that mobile game.