Yes financial capital is just rent extraction (rent on ownership of money like ownership of land). You can make exactly the same argument surprisingly with a temporal labour theory of value (by temporal I mean the version exposed by James Mill and the elder Torrens) where time is discounted by the interest rate, and avoids the ricardo capital problem. In this you trade labour time today for discounted labour time tommorrow - over a full working lifetime, exactly as you would do if you were constructing fix capital which depreciates. Ill do a spreadsheet math example on my blog which shows exactly the trade off between time invested in developing human capital today and future income over a lifetime. Interestingly towards the ZLB it becomes rational for many who can afford it to give up work to study leading to less production.