I'm the other way around... the EF and electronic cameras depreciate significantly over time as the electronics break down or fry or just get old and obsolete. On more manual cameras I think the value is worth the effort more, because it won't break down faster. It will last.
'Course that's just me. I like manual focus cameras. I have an AE-1P. I do agree with throwing good money after bad, though. I've reached that limit on my current defunct A-1 (it was a gamble that I lost)