Every MPLS network requires a local loop to connect from the carrier POP to the customer facilities. Depending on your distance from the POP, the loop cost increases in a relatively linear fashion.
Some companies with multiple buildings or campuses in a city may have OC-3 or OC-12 SONET networks in operation. If these networks run to the POP used by your carrier, you may be able to eliminate or dramatically reduce your local loop charges through the use of a simple cross-connect.
Since local loops are the weakest link in any wide area network, this approach makes a great deal of sense if the option is available to you.