(or: http://tinyurl.com/dl9nh )
(or google maps: http://www.google.com/local?f=q&hl=en&q=from+1563+Cable+St,+San+Diego,+CA+to+16935+W+Bernardo+Dr,+San+Diego,+CA&btnG=Search or http://tinyurl.com/7ogoc )
I hop on and do 65mph the whole way; my 2005 Prius gets high 40s to 50mpg:
For comparison, my 1995 Subaru Legacy L Sedan (2.2L AWD) got 22mpg with much more aggressive driving habits on exactly the same commute; driving that car with new habits got me about 30mpg, although I didn't have a chance to compare the exact same route.
To compare the payback rate for the added cost of the hybrid, you have to establish a base. For the Prius, there is no non-hybrid version, so I compare it against a base Camry. (Others compare it against a slightly-upgraded Corolla; I think that size- and feature-wise, it is closer to the Camry.) The difference between a base AT Camry and a base Prius is only about 2-3k$.
If we assume the Camry gets 30mpg on my commute, then the Prius saves me .66 gallons of fuel every day (1gal/day in the Prius vs. 50/30=1.66gal/day in the Camry). At 2.50$/gal, that's about 1.65$/day. 250 working days a year means 415$/yr savings on the commute. So if the difference is 3k$, you won't make it up on my commute for 7+ years.
However, that's only 12500 miles; I actually log closer to 19000mi/yr. While the Prius does do worse on road trips, I still get low 40s. Assuming that the Camry would also suffer a bit at those speeds (75-80mph on interstate highways in the rural Southwest), le'ts say 25mpg for the Camry vs. 40 for the Prius. For an additional 6000mi, that's 240gal = 600$ in the Camry vs. 150gal = 375$ in the Prius, saving another 225$/year. 3k$ payback is now less than 5 years.
(Just for grins, though, if gas went to 5$/gal, my 12500mi/yr commute would cost 2080$/yr in the Camry but only 1250$/yr in the Prius, reaching payback in less than 4 years on commute alone; rough estimate of 20kmi/yr total at 30mpg Camry vs. 45mpg Prius, I'd save over 1100$/yr, which would pay back in under 3 years.)
The Highlander situation is a bit different. There are non-hybrid models to do a comparison, although the hybrid has more power than any of the non-hybrid models. Even taking that into account, the hybrid premium is pretty steep: 6k$ for comparable 2x4 models, almost 7k$ for the 4x4 limited:
They're even more similar in highway milage, too, so payback on my commute would take a long time. (The hybrids do offer the promise of substantially better in-town milage, but seeing as I've never gotten over 40mpg in my "61mpg city" Prius in-town...)
However... It's not just about paying back money. Other reasons:
1. Both the Prius and the Hybrid Highlander have lower emissions
2. Prius lets you drive solo in HOV lanes
3. Hybrids in California have 10yr/150kmi warrantees by law
4. Putting my money where my mouth is. Yes, I'm paying the price for being an early adoptor, but I honestly believe in this technology and want to make it succeed.
5. Cool spiffy tech!
6. The Prius, at least, is just darned CUTE.
Other options that are mentioned:
1. Diesel. Not currently available in California (not new, anyway), and not nearly as clean. Some of their advantage comes just from density, too, so you're not really burning less fuel, you're burning less volume. Cleaner fuel is coming, but I don't remember if the emissions rules just get stricter at the same time.
2. Motorcycles. Better economy in some cases, much less utility.
3. Carpool. Fine if it works for you, but differences in schedule and source point have made it untenable for me. (Also, if you're running errands on weekends, you're on your own anyway, so it's better to default to an economic car for that anyway.)
I'm personally facing the dilemma that my wife [deliriumdreams] wants a Highlander, and she's happy with the Hybrid, but I'm not so happy about (1) SUV and (2) 40k$ price tag. If they made a hybrid Sienna [mini-van], especially one with AWD, that would be much my preference. Convincing her, on the other hand... :)