This is absolutely true - honeybee populations are already bouncing back thanks to numerous counter measures, but native bee populations continue to decline. Honeybees cannot pollinate all native plant species native bees do, and even when they can, their generalist nature makes them inefficient for many plants.
In net, the transaction is for 27 sheep, with 25 being kept by the troll father and 2 by the troll sons, so 25+2=9+9+9.