Why are they so bad after 100k?
My car is on 223K miles and is still running perfectly.
Well, that's a BMW, so I'd be surprised if it wasn't running at that mileage.
Well, it's not necessarily true that Subaru WRXs or STIs (I'm only talking about these here, your standard Imprezas and other Subaru models are very reliable cars and will last forever if the rust doesn't get to them first) are fragile and will break in higher mileage. What I mean is that, being as expensive as they are, people tend to avoid high mileage cars. Based on my experience shopping for the cars I noticed very early on that STIs with over or close to 100k were significantly lower value than ones with less. I'm talking $4000-5000 less.
For example a quick Ebay search came up with this 2004 STI for $14,500! Same car as mine other than color.
Link Edit: I just realized that $14,500 price is the starting bid, but still. That's a low place to start. I've seen STIs for sale at $12,000 before.
That's ridiculous! It has only 83,000 miles. I bought mine at 50,000 miles a year ago for $5,000 more than that. Sure, any car depreciates with mileage, but these cars seem to do so worse. The "high end" Subarus are so easy to beat up. That what they were built for, so people are quick to assume that these cars were driven hard all the time. Which makes them a tough sell with high miles.
I can't speak for other countries. STIs are very common in the US which gives you more options to choose from, thus prices are all over the place. Australia, maybe they aren't as common? I've checked out STI prices there a few times and the value tends to be around the same mark no matter what. Not to mention that they're all super expensive there to begin with. The UK? I expect the prices there to be higher too, considering the STI will no longer be sold there.