what's the going rate for 16inch goodyear tires, installed

sorry for the lack of information - I can get more info from the existing tires and RV sticker later today.

Ancillary question: do they need to be balanced?

From the brochure:
Unloaded Vehicle Weight: 9255
Hitch Dry Weight: 1752
GVWR: 12192
Cargo Capacity: 3357
Length: 34’7”
Exterior Width: 8’
Exterior Height: 12’6”
Fresh Water Capacity: 46
Grey Water Capacity: 42/42
Black Water Capacity: 42
Furnace Size (BTUs) 34000
Tire Size ST225/75R15(D)


thanks!