[jonreem]

The time-value still comes into play in the form of eth transaction fee. If you're flash loaning to take advantage of an open arbitrage opportunity there will be other parties trying to take advantage of it, so you will pay more to get your transaction in before theirs.

For a lot of transactions like this its actually miners who can detect and rewrite these transactions to take advantage of the arbitrage opportunities first, for this reason this cost is called "miner extractable value" or MEV.

However, note this fee doesn't accrue to the lender!