Is it possible that this experience was influenced in any way by the fact that they're trying to find a "Senior iPhone Developer" for under £40k? That's ~$65k, and thus roughly $100k shy of what you'd need to offer before you started to pique the interest of any good iPhone Developers in the current market.
This is the same thing I think every time someone says "Why is it so danged hard to find a developer that knows SEO or an SEO who can program their way out of a paper bag. It's like nobody has even heard of any, when we'd gladly reward any with $80k and all the soda they could drink!" If you think you are paying market, and you can't find a candidate despite using all the normal channels, you by definition are not pa…
I've been in this field for too long, and can bring too much value, to sell my services at way under value, even if it includes a lot of free drinks.
It's hard for companies to recognize extra value they could possibly be getting from senior/older developers, but also requires a commitment that they actually try to get extra value from them. Whether that's proactively, or just reacting positively to observations/input, and I've not found many companies interested in doing that. It's cheaper/easier/faster to hire the younger kids looking for their first or second job. That used to be me, and I understand those advantages, but I also see the problems associated with those sorts of hires. An ideal org would have a nice balance of all experience levels, but few that I run in to have that balance.