Wow... I should start exporting ghost shrimp... You get them down here 10-12 for $1 and most pet shops throw in half a dozen or more for free...
But yeah to the original question... when ever i buy feeder fish i also buy shrimp and toss them in... This is usualy once a week and there are always 3-4 shrimp left from the previous week. Seems they make good snacks during week days...
I dont know if they would make a good main diet for most fish though.