You can get margin rates as low as a mortgage or even substantially lower[1]. If you don't want to switch brokers you can also ask your current broker for a discounted margin rate. I've heard anywhere from $250k to $1m total assets is enough for them to consider discounts. However, margin calls are a lot more terrifying than foreclosure proceedings, that's for sure. As such, it's virtually imperative to appropriately hedge and that should be factored into the cost of borrowing.
I was unaware that IB's rates are so low. From reading about it, it looks like they make the money back on other fees, including inactivity fees and commissions. So the real rate is not really as low as what it says, although I suppose on large accounts those fixed fees would make up only a small fraction of the total value. Either way, I was wrong about there being "no" options with interest terms as favorable as mortgages. There is plainly at least one. Your point about hedging is well-taken, also.
[1] https://www.interactivebrokers.com/en/index.php?f=18069