This is a good question. It looks like Kalshi (which hosts the underlying market in question here) in fact does pay interest on both cash balances and open posi

This is a good question. It looks like Kalshi (which hosts the underlying market in question here) in fact does pay interest on both cash balances and open positions, at a reasonable market rate: 4.05%. https://kalshi.com/blog/article/interest-cash-open-positions https://kalshi.com/blog/article/interest-cash-open-positions