Except as prohibited by section 237.60, subdivision 3, prices unique to a particular customer or group of customers may be allowed for noncompetitive services and for services subject to emerging competition when differences in the cost of providing a service or a service element justifies a different price for a particular customer or group of customers. Individual pricing for services subject to emerging competition may be allowed when a uniform price should not be required because of market conditions. Unique or individual prices for services or service elements in effect before July 1, 1989, are deemed to have been approved under this section.