The table ExtendedPrice expects the following:
All columns have to have something except ExtensionData which can be NULL or blank. CreatedOn defaults to GETDATE() ie now, CustomerLevelID defaults to 0 and ExtendedPriceGUID defaults to NEWID(). It's not interested in ProductID.
INSERT INTO [AspDotNetStorefront].[dbo].[ExtendedPrice]
So you'll need this in your spreadsheet:
This is for v184.108.40.206 db. Not tried or tested. I urge you to try this in a test db first.
="INSERT INTO ExtendedPrice VALUES (NEWID()," & B2 & ",0," & C2 & ",NULL,GETDATE())"