Unless you have a really cool shop, I doubt your covered under the lifetime warranty.go to an authorized directed dealer. generally if the company authorizes them, they must be decent plus you are covered under directed's lifetime warranty
I would say warranty and piece of mind. You'll know it will get done right and if anything goes wrong, you just take it back. Im not trying to discourage you but its not a walk in the park and with a bad installation, you might as well not have an alarm. Shop around, ask shops if they'll honor the lifetime warranty if you pay them to install it. When I was looking for an installer, I went around to a quite a few shops, spoke to a few installers and asked one I liked if he would do it as a side job..maybe you can try that.So the high prices really arnt high its just that your paying for the warranty?