You don't need to buy any kind of license upgrade for this to work. I just had the basic 5505 model with the 10 user license.

The steps I outline above will get the ASA ready to talk both to Macs and iPhones. Once you've gone through everything above, then you just need to add a new VPN configuration on the iPhone and match up the fields with the options you configured on the ASA. Make sure you select Cisco IPsec on the iPhone when setting up the VPN. Otherwise it's pretty straightforward. You have nothing to lose, might as well give it a try. If it doesn't work, then you can always reset the ASA to it's factory defaults and start over.