Simple. Accuracy and volume.
Maybe 50-80 data points per day are handled by an internal employee. A trained research team that verifies thousands and works with layers of verification:
An ecommerce company based in the USA Hire Web Research Services Companies outside the country to keep track of prices. They were able to recognize 11 pricing disparities within a 30-day period, and modified their catalog. That quarter alone marked an inflation on revenue of 18%.
This sort of outcome can seldom be achieved by a 2-person in-house team.