Hmm...did a google search, and I could only find one reference to honeybee stomach size, and that was that a medium size load for a bee was 12-15mg. I can't verify that. Since that is a weight, and nectar, water, and honey all weigh different, there isn't a good conversion to volume, that would be around .003 tsp.
That is roughly 1000 bee trips for a tsp, and while that seems high, if you stop and think about how many bees are around, and how many trips they take, I don't really think that is outrageously high. If you have 20,000 bees in the hive (assuming early spring) and half of them are foraging, that is 10,000 bees at a time that are collecting nectar, they can make quick work of 10 tsp's.
I don't know if the math is correct, but if its not, I'm sure somebody will correct it :-D