I actually interviewed for a contractor position at a place last year which was on HN who's hiring. It's a big place and had a good team but they offered well below market rates. I pushed on this an they came up a little (nowhere near enough to entertain). Instead I was greated with an offer to make it up via overtime. I believe the phase was something along the lines of "there's no shortage of work and we don't cap the number of hours you can work per day". I really liked the guys but I thought that was totally disrespectful of my time.
I would be actually ok with that provided that they offered to pay for the overtime. I think they told you the rates they are willing to pay, and left the number of hours up to you. This kind of arrangement works for me. There isn't anything shady going in the background(paying for 20 hours, expecting 60 hours). I have an option to take it or leave it, but they aren't trying to offer a "t&c applied" deal.
I get what you're saying, they're not hiding anything - but you're still losing out. Instead I took another contract for 2.5 times as much - and I was working a lot of overtime on that contract.
You have a finite number of hours in the day, and your life. Don't give them to someone else to profit off. That's crazy.
I am not advocating letting someone use(exploit?) you for his own profit. But I like free markets and I am saying if the employers aren't doing anything shady and just offering low salary, someone who finds the salary good enough can take it.
Recontextualize this for a minute and let me see if it still makes sense.
The company offers a salary of $50/hour when he thinks his market rate is $100/hour. He refuses, countering by asking for $100. The company comes up to $60. He refuses. The company makes the following final offer: "OK, you win. We'll pay you $100 per 1 hour 40 minutes and you can work as much as you want." How have they bettered their offer? Especially when there are (presumably) other market rate jobs out there.