I've thought along somewhat similar lines of 'resource budget' before, and can't find anything obviously wrong with that argument. That is possibly because I haven't quite defined 'resources'.

The AI danger crowd seems happy to assume that the AI wants to maximize its available free energy, so I would assume they're similarly happy to assume the AI can measure its available free energy. I do agree that this is a potential sticking point, though, as it needs to price resources correctly, which may be vulnerable to tampering.