>If you offer more to depositors than you charge borrowers, it's never sustainable you're making a loss.

Only if the amounts being borrowed and loaned are exactly the same.

I.e 20% on $100 is less than 10% on $1000

>If you offer more to depositors than you charge borrowers, it's never sustainable you're making a loss.

Like a sibling comment you are not accounting for the profit that comes from the collateral.

Maybe a nondefi example would help. Imagine if a landlord got a loan using a rental property as collateral. In this example the lender will now get the payments of rent. Now the lender makes money from both the interest rate on the loan and from the renters of the property. Depending on the demand for the rental property the amount of rent you may collect can fluctuate. This means that some months you may make more money than others. So in order to sustain a certain level of profits the amount of rent you collect will need to be worth a certain amount.

That’s not how it works in the real world though. A landlord takes out a loan at a particular interest rate, and makes repayments based on that. The bank doesn’t “get” the rent, they get the repayment that ideally for the landlord is less than the rental income, unless they’re relying on capital gains. The collateral only comes into account if the borrower defaults, for the lender to sell to make back what they were owed. Otherwise they have no claim on anything to do with the collateral - neither the rent nor capital gains.

I was just trying to make up some sort of example where you can gain income by holding on to someone's collateral. I wasn't trying to say how something typically works.

That isn't how collateral works, so you really are just making stuff up. If you did start doing this sort of thing as a bank you would attract regulatory attention pretty quick.

You're basically talking about reypothecation[0]

[0]: https://www.investopedia.com/terms/r/rehypothecation.asp