Most of the assets for big name games are built using one of a few large outsource studios that are capable of providing hundreds of staff for a project. internally the number will be much smaller. Turnaround time for an average set of modular props will be anywhere between a week and a month.
On ave, the percentage of modelers to the entire studio is very low. And most studios aren't 500 people. They will be MUCH smaller...even the larger ones. Maybe teams like Ubisoft and Rockstar would have that many between multiple studios. A lot of places quote larger staff numbers because of the amount of outsource groups…