Talking about collecting things - when I was working for a certain local authority, the lads whose job it was to clear houses found a room full of shoe boxes. Every box had a date on it. Inside each box was a turd.
I have a friend in the antiques trade and she says it isn't exactly booming. For example, even the most beautiful china tea sets are only worth two or three quid. (This astonishes people who rock up with Royal Doulton or whatever, expecting it to be worth hundreds.)
A lot of it is indeed about memories. A bit back she was selling clockwork trains for stupid amounts of cash. But the generation who had them has largely dropped off the twig, so now they're almost worthless and she's given up selling them.
Some stuff does have inherent value - but it's largely top-end that few of us have hanging about. Silver and gold, of course, is always saleable, but the market goes up and down.