I work in sourcing for a mobile phone repair company in the South Island.
I can confirm that the actual cost of the replacement display assemblies for iPhone 5 are around $250-280 USD per unit. These are for original Apple parts as third parties are still gearing up for manufacturing of the third party touch panels.
My recommendation is to go through the Apple service program - call 00800 76667666. Cost is around $360 for the service and carries on the existing warranty.