How many wasps are in a average bee hive?

50,000

a single hive will usually contain:

1 queen

~60,000 larvas (upto 2000 hatches a day)

upto 100,000 workers.

upto 2000 drones.

all depends on the hive location (amount of pollen -> nectar produced)

and the time of year (just enough to survive the winter, and in abundance in spring).