The GetSKUFormattedPrice takes different parameters in Kentico 9. In K8 it took no parameters at all, but in K9 you now need to specify whether the discounts and taxes should be applied and the column name of the sku price.
You can call it like:
<%# GetSKUFormattedPrice(true, true, "ColumnName") %>
You can also find more information here (just search for the GetSKUFormattedPrice)