OK, the definitions are starting to sort themselves out in my mind, and the confusing issue is that not all collectibles, cult or otherwise, actually increase in value, especially not above their new purchase price. Arthur's "new" VW bug, for instance, is very collectible but still not expensive (though not always quite as cheap as he got his!), so someone who bought one new as an investment probably still can't cash out for much.
I mean, sheesh, how many purchasers of the 70 Chevelle were thinking investment? That's how unpredictable this question is.