The Prius batteries (which have been in use in the Prius by the thousands for over 8 years) show no signs of actually requiring replacement after only 8 years. They are really quite coddled by the control system (minimal depth of discharge and good charge management) and likely to last the life of the car (200k+, as a few already have). The fear of a big cost to replace the battery appears unsubstantiated and I have no idea where the incorrect 'oh, you'll have to replace the batteries' meme even started. It's not a flashlight - the batteries seem to be about as reliable and long lived as automatic transmissions (actually moreso in my unlucky experience), yet no one factors in the cost of replacing an automatic transmission after 10 years/150000 miles (the length of the Prius battery warranty in CA). If you don't believe the Toyota engineers about the battery pack, "We have lab data showing the equivalent of 180,000 miles with no deterioration and expect it to last the life of the vehicle," nor trust the 8 year in-the-wild record, or find comfort in the decade-long warranty, then I guess you should budget in the cost of replacing the battery pack. In the same vein, I will budget in the cost of a new transmission for the next Ford I buy (which will be around never, unless its a '65 Mustang fastback - I have a softspot for rolling art).

The problem with hybrids is the extra cost (and the waiting lists). The cost is a real issue, which I think was actually the main point of your original post. But I have yet to hear a single supported concern about hybrid technology that has any legitimate factual basis.