Your error in this statement is that you are assuming the used car is not also financed. I've got news for you, if someone needs to finance a $35000 new car, they also need to finance the $25000 used one.
This is absolutely a consideration, and I pointed it out earlier in the thread. You CAN get 0% or 1% financing on new cars, which, compared to buying used, may end up a 'push' on your overall costs (depending on what your used car loan rate is, probably at least 4% or more).
So, it does make sense to run those numbers, because if you're going to hang onto the car (new or used) for 5 yrs or more, that loan interest difference could end up being about the same as the depreciation difference (or close enough that you don't care). Run the numbers for your case specifically, so you can make an informed financial decision and not just a 'Wow! 0% interest is awesome!' decision.
On a 5 yr, $25k loan at 4%, you pay about $2800 in interest, so that's the number to compare to your expected depreciation difference and repair costs difference. Thus, if you were looking at a new Subaru at $30k vs 2-3 yr old used at $25k (probably more like $21-25k, which makes the loan interest $2200-2800), you can look at the depreciation differences over the 5 years to make a good guess as to what you'd actually save. If you use 3 or 4 yr loans, the interest amounts are even less.