Shopify doesn't have a "Sale Price" field in the backend. It instead uses a field called "Compare At Price" which basically makes the regular "Price" as the sale price if the "Compare At Price" is specified.

So the logic is basically:

Make the "Price" field the "Sale Price" only if there's a "Compare At Price".

EZ Exporter supports conditional logic in Calculated Fields, so you can use these formulas to add a "Price" and "Sale Price" column depending on whether a "Compare At Price" is set:

Price

{{ variants.compare_at_price }} if {{ variants.compare_at_price }} else {{ variants.price }}

Sale Price

{{ variants.price }} if {{ variants.compare_at_price }} else ""