I don't understand the Apple One + extra storage pricing

I am currently subscribed to the Apple One service, and I am looking at adding extra storage.

The plan is called 'individual' and I get Music, TV, Games, and 50 GB storage for €11.95 / month.

Then there is the 'family' plan, which has the same features but 200 GB storage, for €16.96 / month, and you can share the plan with up to 5 people.

The price difference is €5/month.

For €3/month, I can add 200 GB of storage and have a total of 250 GB for €11.95 + €3 = €14.95 / month.

In the end, I can get:

• individual plan with 250 GB for €15/month, or
• family plan with 200 GB for €17/month.

But, while I'm on the individual plan, there is already a family sharing feature that is enabled. I have my daughter in the plan already.

So, I'm not understanding the pricing at all. Unless, 'family sharing' on the 'individual' plan is not the same feature as 'family sharing' while on the 'family' plan.

This is very confusing...