Its a search for rare items. Does not always mean you will find rare items. You need to look at the bigger picture: Given 1000 returns, what % of those returns are actually 'rare' items, and what are their worths.
Remember, this is a game of 'little' improvements here and there, which add up over time. If each rarity search brought back 100 beans, it would kind of negate the need to do any adventuring at all :P