You should also remember that if things go wrong, it is easier to get redress if you have booked a package.
1. By law, all tour operators are required to provide financial protection for consumers. So if the operator goes bust, you will get your money back if you haven't travelled or will be brought back if you are abroad, at no cost to you. If you book independently and the airline goes bust, you may be able to claim from your credit card company if you paid by card and it cost more than £100, but incidental expenses (hotels, car hire etc) are unlikely to be covered.
2. If you have a problem with the hotel and can't sort it out while you're there, you can pursue the operator once you get home, and go through the smalls claim court or arbitration if you can't get satisfaction. It would be more difficult to pursue a case against a Spanish hotel in the the Spanish courts.
I'm not saying that this justifies the prices that tour ops charge - or that things are more likely to go wrong on a holiday booked independently! - just that this is another part of the mix that is often overlooked.