Yes, the barrels interchange. Yes, $200 is a super price. You can find used 1100 barrels on eBay. 1100 receivers come in Magnum and Standard versions. Both the 2 3/4" chamber barrels and the 3" chamber barrels will fit on either receiver, but you should not fire 3" shells with a Standard receiver. A whole range of barrels are made to fit the 1100: fully rifled with rifle sights, rifled with cantilever scope mount, smoothbore with rifle sights (for turkey), smoothbore with cantilever scope mount (for turkey), vent rib barrels from 26" to 34", barrels with interchangable chokes. Skeet barrels, trap barrels, Hastings even had a .50 Black Powder muzzleloader barrel to fit the 1100 that utilized the 209 primer.
The foregoing assumes you are talking 12 ga. You cannot change to other calibers (20 ga, 28 ga, .410) by simply changing barrels. There were even left hand 1100's, and the left hand barrel will not fit a right hand receiver. Light target loads may not reliably cycle in a 3" Magnum barrel.