Agree. What we need to remember is what we are talking about is very old electronic equipment. This is essentially worthless - go to a car boot sale and you will find plenty of 70s and 80s electronics going for the price of a sandwich. B&O has the advantage of build quality and rarity and a dedicated bunch of idiots who collect it! None the less, relatively few pieces are really worth any money and this will be because they are particularly sought after or fabulously rare.
The Beomaster 4400 is IMHO the best receiver made by B&O. Beautifully made, classic design and superb sound. I have had three and never paid more than £75 for one. The one I have now is actually a 4401 and was a most kind gift from a good friend. That would be worth a lot but because it is rare, not because it is any better than any other 4400.
The Beomaster 8000 is the most powerful Beomaster. I have had two and paid over £400 for one of them. This is because they are rare in good condition and complete. Is it five times better than a 4400 - actually I prefer the 4400! But it is worth more because of demand.
The Beomaster 3000-2 is a wonderful amplifier. But it is not the biggest or best sounding (though it is very sweet sounding) and they made thousands. I got mine for £30 in perfect condition. Not sure what I did with it - hopefully someone is enjoying it still!
The Beomaster 6000 quad is actually not as good sounding as the 3000-2 but is worth considerably more because they were very expensive, all broke and most were thrown out. Those that are left have usually been looked after and are rare. Hence they are worth a lot.
However on eBay, it always astounds me when things sell for huge sums - put in a good advert and good pictures and hope you get two people bidding against each other!