So throughout the 80s, PC stuff was wicked expensive compared to buying an amiga. This persisted well into the 90s.
By 1994 for the price of an 040 A4000 you could pick up a PC that spanked it seven ways from sunday for the same price. Sure, the OS may well have sucked balls compared to AOS, but it got the job done.
I don't know about other markets, but by the time AGA Amigas came out, the market had already made huge strides both in terms of performance and value for money here in the UK to the degree that the Amiga really wasn't relevant any more.
I know amiga upgrades were pricey, but is there something I am missing, or was PC owners just being robbed?
New things cost more, as they become less of a niche the larger market drives costs down. Consider that you can now pick up GSM phones for £7 new in supermarkets here in the UK, to get the same capabilities 10 years ago when pay as you go cell phones first started getting popular you'd be looking at £60+.