I want to show a custom (not computed) discount for each variant of a product for a limited time.
Each variant has a different original (not discounted) price. When I add an extra line in the same pricelist, and put a discounted price (which is less than the original that is in the same pricelist, so there are two items for the same variant) it shows on the website as expected. 

However, this only works for the cheapest variant. When I do the same with the next variant in the list (i.e. bigger size) the strikethrough price that is shown is still the one from the cheapest variant. The discount then seems smaller than it actually is. Another way to see it, is the strikethrough price is always the same, but the discounted price increases correctly. As I do this more than four times, no strikethrough price is shown at all (but the sale price is still correct):

discount price A -- strikethrough price A works fine
discount price B -- strikethrough price B doesn't work correctly, because it shows strikethrough price A instead of strikethrough price B
....
....
discount price G -- strikethrough price G doesn't work at all, as it doesn't show any strikethrough price. 

Why is this happening? I don't understand why Odoo always shows the same strikethrough price and then stops showing it at all. 

Is there a way to show the correct strikethrough price for every variant, like any other website software would allow to do easily?