We purchase fluids in many different container sizes, and they are sold/used in manufacturing by the Liter.

So for example we may purchase, all from the same vendor, a 20L drum, a 205L drum, a 1040L container - all of the same fluid, but with a different per liter cost for each. 

E.g. Vendor A sells:

• 20L Drum @ $20

• 205L Drum @ $200

• 1040L Container @ $1000

I want to set up vendor pricing for each size, but once purchases I want the system to recognize how many liters we have, i.e. these should all be treated as the same product, just purchased in different package sizes at different unit prices. A purchaser should be able to select between the various packaging sizes and have the purchase price adjusted accordingly.

There doesn't appear to exist an option to purchase in multiple different UoMs.

Packaging options appear to only apply to Sales and not Purchases

Product variants don't work because they don't retain the relationship between the different packaging sizes

I am at a loss here - I don't think Odoo can do this without significant customization but thought I would ask...