Have communications with Developers Support and Code Level Support about this during few last weeks (every response got a lot of time) - no result.
First, Code Level Support assistant redirect me to this topic :) and quoted nick_js post where he suggest to contact Developers Support to request "com.apple.developer.financekit" entitlement.
Developers Support replied on my request this: "The entitlement form is not available yet.".
So how does others apps can use FinanceKit?
All this means that FinanceStore framework is publicly available, but can't be accessed by everyone right now.
Only three Apple-chosen apps (Monarch, YNAB and Copilot) have access to it, which looks like discrimination of others developers and unfair play.