PO, Accountabilities and Budget

Hi there,

I am back again with a recurring discussion of the agile budget.

• The scrum guide does not mention budget (at all) as accountability of PO.
• Budget is not defined or discussed in any context in the professional scrum competencies.
• But the official scrum training for PSPO includes budget in accountabilities list of PO.
• The forum blogs and the book "professional scrum product owner" by Don McReal and Ralph Jocham mentions 5 maturity levels of PO and recommend that ideally, PO should own the money decisions.

My question now:

1. If budget is the accountability of PO why is it not in the scrum guide or competencies list?
2. Is the budget recommended to be owned by Po or "must" be owned by PO? (I know it is a framework and needs to be adapted in a specific situation). When we say someone is accountable for something that means this duty is not to be with someone else. And if it is that sort of item why it is taught in the training course and not mentioned in scrum the guide?
3. In scrum (team) there are only 3 roles (developer, SM and PO) no other role is defined or discussed how does it work in a scaled-up environment, does NEXUS have more roles? For example, there is a big final product let us say a CAR and there that is divided in small products let's say ECUs. The POs own ECUs as a product then who owns the car as a product? again a PO? or a product manager or who? and who owns the budget here? the ECU POs or the CAR PO?
4. How is the existing hierarchical organization linked with a scrum team, finance HR etc how PO interacts with them?
5. IF PO is the ultimate entrepreneur and CEO who is the resource manager? PO? 

Rehards,

Aamir Shakoor