Apple pay couldn't be any easier (that chip thing on my credit card is a nightmare)
Ok, that may be a US thing - I know your businesses are making a meal of the change to chip'n'pin, which has been working nicely in the rest of the world since forever - and for small transactions, contactless is now taking off. Not sure I'd trust Touch ID as anything more than a 'convenient' alternative to not bothering with a lock code... (very conscious of the fact that my greasy fingerprints are all over my nice shiny phone, so they're hardly 'secret') - Apple Pay looks nice but not must-have & I don't want my credit card to ever run out of batteries.
Which wouldn't even be a problem if it weren't for exaggerated growth expectations
That's part of the problem, but the real problem is that all phone sales are going to tank now that phones are good enough so that people stop upgrading them every 18 months and realise that means they don't need to get their hardware on contract.
Also, when the iPhone was launched it was so far ahead of the competition* (even with the no-3G, AT&T only thing, which was only ever a bootstrap) that they had a couple of years to get the kinks out before Android became a credible competitor. There's a ton of credible competition to the Watch.
(* I once had a pre-iPhone Windows Mobile smartphone - it was awful)