Are payday loans really extortionate?

To make a long story short I work a not so great retail job to support my disabled wife and son. Last week I got hit with that horrible bug that seems to be going around and I fought hard to stay in work throughout but I had to eventually take one day off work. That one day was enough to basically completely screw up my budget for the month as far as rent, food, electric etc as we have no savings and live very much paycheck to paycheck. I'm now about £85-90 short for the month and panicking tbh. Are those services that you can borrow short term money from extortionate or dangerous? I don't want to get into debt or put us in a position we can't get out of but I'm so worried about how I can fix this somehow. Thanks for any info anyone has.