I went through this exact same thing with my wife. She has problems and we went to a guy that played the same sell. They tried to put us on a 6 or 12 month routine too, and for about the same money you're talking about.
We skipped it, went to a different chiro who also used a lot of massage therapy. Adjusting her occassionally and lots of therapy have gotten here in good shape. It was a big drain up front (claimed over $4,000 on her expenses in 2008), but after a few months, it slowed way down to a massage once a week, then every other week, then "as needed" with an adjustment thrown in every once in while.
To me, they don't cure all, but if you have actual back problems, there aren't a lot of good options. A regular doctor is typically limited to doing surgery or giving you drugs. What else can they do? For me, I recently had some really bad back problems that caused my arm and shoulder lots of nerve pain (all the way down to my hand). At times, the muscle spasms and nerve pain was some of the worst I've had. Went to the chiro, got his advice. Then I went to the doctor. The doctor said he doesn't like to just throw drugs at a problem, but prescribed me three things. He gave me an anti-inflammatory, muscle relaxers, and hydrocodone. I also laid on a heating pad at night after taking the meds. 10 days later, no pain, no issues at all.
So for me, the drugs worked. For the wife, the adjustments and physical therapy worked. It should be noted, in reference to your wife's desire to see the hot wacko, while we were spending $4,000 for adjustments and treatments, my wife had normal illnesses that anyone would get anytime. She had the flu once, regular colds, sinus infections, upset stomach (over the course of months...she's not sickly). So if the chiro was the "fix all", why was my wife experiencing normal life illnesses while being treated?