The unlimited offer is simply a marketing tool used by larger companies to attract those new to hosting or unaware of the problems it causes. However you wouldn't see a computer sales person recommending a computer due to its "unlimited, CPU, RAM and Hard drive" which essentially these hosts claim, and yet many fall into the trap somewhat.
As most know the limitations are laid out in the terms of service and as human nature we don't as consumers read such documents, remember the "next, next, next" of installing a program
The price suggestion was more for "your" advertising/packages rather than anything else as many firstly try low prices with resellers and then realise that the support is if anything what will make the difference, ontop of the usual expectations of a client.