Commercial bike tours through wine country come in various styles. Costs range from less than $100 for a day trip to a few thousand dollars per person for a top-of-the-line tour lasting a few days with high-end accommodations.
There are two basic types of tours, with variations:
Self-guided touring. You pay a tour company to do the research for you, plan routes and wineries stops, and book your accommodations. The details are taken care of, but you're free to travel at your own pace and with chosen companions without being part of a larger group. For an extra fee, you may be able to have your luggage moved from stop to stop. Some companies offer a range of standard tours, but others will plan a custom tour for you.
Fully supported touring. This is the luxury option: The tour company does everything but the cycling and the wine tasting -- they plan, provide accommodations, book at least some of your meals, transport you and your luggage, take care of breakdowns or injuries, and even provide water and snacks. You may be part of a larger group or pay premium rates for a guided tour for your party only.
Most tour companies offer bikes and helmets for rent for those who may not have road-quality bikes or don't want to transport equipment.