Every loaner is different, based on mileage and depreciation from time in service.
They are less expensive than new. I will only quote loaners that are available to interested parties, there is no “General Number” as a car that was in service for 4 months experiences more depreciation than a car that was in for 12 days.
Also, you have options of not counting existing mileage against a lease or counting it against the lease. These variances create real swings in cost, hence real changes in price.