I think as soon as you're married it's a good idea to get wills prepared - if you meet a sudden, untimely demise, it'll be much easier for your spouse to deal with things if you have your affairs in order (and vice versa).
A lawyer's fees for "mirror" wills for a couple shouldn't cost more than $500 or so, depending on the area of the country you're in. Bear in mind that these fees aren't standardized, so it pays to call around and get a few quotes. It'll cost a lot more than a "kit", but it'll generally help to avoid problems after you're gone - lawyers use complicated language, but the reason for that is (in part, at least) to avoid any ambiguity in the meaning of what's in the documents.
