the onChange code is not correct.
change:
onChange="document.WADAInsertForm.ProductSKU.value = document.WADAInsertForm.ProductName[document.WADAInsertForm.ProductSKU.selectedIndex].text;document.WADAInsertForm.ProductPrice.value = document.WADAInsertForm.ProductName[document.WADAInsertForm.ProductPrice.selectedIndex].value"
to:
onChange="document.WADAInsertForm.ProductSKU.value = document.WADAInsertForm.ProductName[document.WADAInsertForm.ProductName.selectedIndex].text;document.WADAInsertForm.ProductPrice.value = document.WADAInsertForm.ProductName[document.WADAInsertForm.ProductName.selectedIndex].value"
also, the select list value is still set to use the ProductID column, it needs to use the Product Price column for this to work.