If you've done them already then you know it's going to cost you around $300-600 for a decent set (e.g. a pair of E46 for example) with the ballasts and bulbs. Slightly more if you go bi-xenon. You'll also need the harness which probably runs around $60-100 depending on the source.
And if you want an OEM look you'll need to fabricate a decent set of bezels to hide the projector bodies. Most folks seem to modify bezels off of other vehicles that had stock HIDs which means you need to buy those lamp housings at a boneyard.
If you're handy you'll probably save yourself a couple hundred bucks. But after seeing the difference in quality between some of the home-brewed HID installations and the professional conversions, I'm biased towards just letting a pro do it for me.
I planned the same conversion. Then after reading about the number of people who invested in HIDs only to have to rip them out later to pass inspection....I decided to buy Kolak's lighting upgrade instead.
12 Wrangler Sahara JK8 conversion, <10 miles (FOR SALE, $56,700)
01 WJ Limited, 4.7, 247, black on black, 157k miles (sold)
96 XJ Classic, 4.0, 242, black on grey, 267k miles (sold)
00 XJ Sport, 4.0, 242, fern green on grey, 76k miles (sold)
90 XJ Wagoneer, 4.0, 242, burgundy on tan, unknown mileage (sold)
97 ZJ Limited, 5.2, 249, black on black, 138k miles (wrecked 12/15/05)
98 ZJ Limited, 5.2, 249, burgundy on black, 197k miles (sold)