In my case I went from a 192,000 mile, 20 year old Mazda 323 to a 95,000 mile, 11 year old Mazda Protege. And when you throw in the $1,000 from the state the Protege only cost me $900 ($1,900 total). So by comparison I got 97,000 less miles and a 9 years less wear and tear advantage over the old car for my $900.
I've already gotten 6 years and 33,000 miles out of that Protege. And at only 128,000 miles and driving no more than 5,000 miles a year it may well go another 6 years +. BTW, the $1,000 comes for a small fee attached to everyone's registration. The money pool is only so large and once it's gone the opportunity is also. At the time my paperwork advised me the fund was running low and to turn in the car ASAP. But, yes, I agree about them being a bit "tricky" in trying to get smog exempt cars off the road. And, I wonder what the incentive is for the county, not the state to be making the offer?