A while back, one of the commenters asked about "market rates" for things here in Kabul, including alcohol. Frankly, I don't pay much attention to the cost of things that I buy, partly because a lot of my regular expenses (food, rent, etc.) are covered and partly because I can't be bothered to keep track of these things.
However, for those people preparing to deploy to A-stan or considering a position here, I can say that a surprising array of products are available nowadays in Kabul. Although the quality may be an issue, there's not much in the way of necessities that you can't find somewhere in the city. Prices are a bit higher than the States (approximately equivalent to London) for most things, with a few exceptions.
Proper, authentic booze is anywhere from $75 to $150 USD a bottle, depending on brand. The fake rotgut stuff distilled from Russian brake fluid is cheaper, but you wake up with your intestines in your socks and can't focus your eyes for 36 hours.
Cigarettes, even the premium brands, are dirt cheap, as low as $0.50 a pack for the crappy Afghan/Pakistani brands. Even for the imported high-end smokes like mine, you won't pay more than $2.50 a pack.*
*And by "imported" I mean "fell off a truck in Tajikistan and smuggled across the border in a donkey's rectum." Gives them extra flavor.
Clothes are easy to find around the city, but quality is an issue. My advice is to pack only what you need and plan on buying extra stuff at the Bush Bazaar or one of the small shops. Most of it won't last, but it's cheap enough not to matter.*
*Note that this applies to men's clothes. I have no idea what women would find, unless you like full-body concealment in a fetching shade of blue.
Boots and shoes are a bit harder. Lots around, but most of it won't last a month. If you have access to an ISAF PX, you can get good stuff at a high price, or look for the stolen stuff that finds it's way to street vendors.
If you're going to be in Kabul for any length of time (and not on an ISAF base), do yourself a favor and get a local fixxer to handle the shopping for you. A keyed-in local can help you avoid the scams, negotiate on your behalf and locate those hard to find items like booze.
Under no circumstances should a Westerner new to Kabul try to buy weapons other than a knife. There are plenty of guns for sale, but it's illegal to buy and sell unless you work for a licensed PSC. The Afghans just love to make an example of Westerners and there's a good chance that the friendly guy with five AKs in the trunk of his Corolla is an NDS agent. Even if he's not, he'll sell you the gun (which won't work anyway) and then call NDS and rat you out. If you absolutely have to have a weapon (and your outfit doesn't provide one), find a friend at a PSC or high-up in the Afghan government. Otherwise, you're liable to end up getting the long-term rate at Pul-i-Charki Prison.
Pack some quality Western medicines (sometimes hard to find here) like rehydration tablets and something for stomach ailments, enough personal supplies (i.e. toothpaste, etc.) to get through a week or two, some rugged and versatile clothes and a decent pair of boots or hiking shoes. Pretty much everything else you can find here, or find someone who can find it for you.