Wow, you drive a lot of miles! You'll feel it more than the average driver, that's for sure...
If I drove that many miles, I'd probably have a much more economical vehicle than a 4Runner, just because I wouldn't want to spend that much of my money on gas. Now if I NEEDED a truck or SUV to get me front point A to point B, that would be a different story. Honestly, I could just buy a little economy car and my 98% of my transportation needs would be met....I just don't WANT to drive a car, so I'm willing to pay at the pump for my choice. But if I had to pay a huge amount of money, I might be inclined to switch to a more economical choice some time down the road.
By the way, I used a combine 2.5 mpg difference because that's what the EPA says, and that's about as accurate data we can get. The cost of gas is projected to keep rising, so the difference you stated might be much less than the real difference, especially if gas prices continue to rise, as expected.
Now here's the interesting part-- WANTS versus NEEDS. Just as MOST of us chose a 4Runner because we WANTED it (as opposed to actually NEEDING it), the same thing applies to the V6 versus V8 debate. For MOST of us, there's no reason to choose the V8 other than WANTING it. The V6 will do everything the V8 can, with the possible excpetion of maximum towing ability. But MOST of us don't tow regularly at or near the limit, so it's safe to say that the majority of people who buy the V8 do so because they WANT it, not because they actually NEED it.