We do. Here's the link to the one we use http://www.fullcircle.com/ though we're about 3,000 miles too far away, it's a good way to look.
We pay $36 dollars every other week or every week (depending on whether we want deliver every week or every other week)... which comes out to around either 900 or 1800 per year. It's EXACTLY the same price as if I was buying the fruit/veg from the store (I compared the box contents in their sample orders to what I already paid in store) for our area. In the 2 most popular CSAs locally one can change their order contents online (ex substituting peaches for grapes or chard). We have a list of 12-18 items and then another list of 12-18 substitutes. Ours is produce only (fruit and veg). Meat/Dairy/Egg prices in our area are through the roof ($10 per pound for lunch meat, $5 for hamburger, $15-20 for steak....milk is $4 per half gallon or $8 per gallon...etc.). I've yet to come across a local CSA that does meat/dairy/eggs... although there are several resources of buying 1/8th a cow, or having milk delivered... they're just not part of the CSAs around here.
Our CSA one pays on a weekly basis and can stop/start/suspend at will (ex going on vacation, or money is a little tight this week or month).