When creating variants, Odoo apparently assumes the variants all have the same values (like T-shirts in different colours). You can change variant prices by creating an EXTRA cost. However, in my case I have a default product that has a set price. In my case, a 1 L of paint. I have some variants that share the same attribute (in my case colour) but not the same other attributes (in my case volume). So, other volume variants, share the same main attributer (colour), but the other values are quite different (in my case 100 ml, 250 ml, which is less than the default 1 L) and 5 L and 10 L (more than the default value of 1 L). It is impossible to create a price variant related to the default volume (I can't use the EXTRA cost). I was considering setting the default price of a 1 L to zero, and then start adding up, but this seems very weird and doesn't show well. How can I solve this? To put is simple, I need to be able to set prices of variants INDEPENDENT of the default value.