That's a perfectly normal price for travel insurance in the UK. Because it doesn't include healthcare when you aren't travelling.
That's a pretty normal price in the US too because it also typically doesn't cover healthcare when you're not travelling or, indeed, non-emergency healthcare at all. Normal travel insurance != global healthcare insurance.
My trick is simple: Get an Amex Platinum if you need insurance for under 2 weeks [1] and buy insurance from your bank for anything longer. Banks compete on trust, so they don't randomly fuck you over. I actually used my bank's health insurance when I needed it and they were nothing but professional. It was RBC Canada, if it matters.
[1] Reach out to me if you do this and we'll both get enough points for a free transatlantic flight.