1) real kits come w/ hid "capsules" and ballasts/igniters. not just bulbs.

2) prices should be around $425+ for new (ave probably $475), and $250+ used.

3) over time, "color shift" occurs and they become more blue and dimmer. but HID bulbs should last you essentially the "life of your vehicle"

4) the more blue/purple light you get, the less "usable" light hits the ground. you'll also produce more glare because the higher spectrum light scatter easier. also the more blue/purple light you have, the less you'll see when the ground is damp/wet/moist. driving in the rain will be like driving w/o lights on.

and one last note of caution, don't buy salvaged HID parts. they're good if: 1) you drive a car with OEM HID that need replacement parts, or 2) you're REALLY GOOD w/ dremels/tools and can make your own 9006 adapter so the bulb will sit in the right place. else, just buy a 9006-kit instead of ghetto rigging one to work half-@$$ed. unless you possess some mad DIY skills.