Yes, margin can be dangerous at times and is not that cheap. About 6% over fed rates, or 11-13% right now. Over $500k you'll probably get a better deal.
But I agree with you about margin borrowing's interest rate not being that amazing, although it is of course cheaper than most credit cards. Vanguard is, as you said, 11-13%. <https://investor.vanguard.com/client-benefits/margin?msockid...> By contrast, my Amex line of credit charges 6%, and I am preapproved for an Amex personal loan for 8.98%. I presume others on HN can get comparable or better.
IBKR is +0.5% at >$200k (It starts at +1.5%)
In any case, my Amex line of credit charges 6%, and I am preapproved for an Amex personal loan for 8.98%. I presume others on HN can get comparable or better.
The Schwab rate sounds high. Fidelity, for instance, charges SOFR + 190 to 310bps [1]. I haven't had an SBLOC for a few years, but I remember Stifel charging no more than 200 bps over Libor.
[1] https://www.fidelity.com/lending/securities-backed-line-of-c...