it will be $50 per support call, even if it's because the machine is broken and you need to get it fixed under warranty.

I guess I haven't come across that. I do know it costs money to talk to Apple to troubleshoot problems outside the 90 days, but I was always under the impression that any such charges would be refunded if pure problem diagnosing ended in having to repair the system.

Easy way around this though, and the hassle of shipping the system off. Find a local reseller that also does support. I have never been charged by mine, even in troubleshooting a really odd and infrequent problem. I have had the screen replaced once (known pressure points causing white spots to appear in the first shipments), and had my right USB port fail to power/see devices (required a tiny 1 inch PCB to be replaced to fix it). Both repairs, I took the system in, showed them the problem, and they ordered the parts. 1-2 days later when they had time, they called be back and had my Powerbook back to me in 30 mins.