Sounds like you dodged a bullet there. "Don't have a computer capable of running a new version of KiCAD"? My work laptop is a dual core I5 with no discrete graphics and it rius KiCAD just fine. Most any fairly basic computer can run KiCAD. If they can't afford that - how can they afford to pay a designer? Even if they accepted your offer, which I agree, you were charging too little based on the information provided, I wouldn't hold my breath waiting for the check to come.
And no schematic at all? Sounds like they were trying to get you to not just design the PCB, but design the whole thing. That's DEFINITELY worth way more than you were going to charge. Are they too poor to even afford some paper and pencils for their 'startup' to hand draw a schematic? Or does no one remember how to do that any more?
I made that mistake in my younger days, undercharging for my skill (in IT work - I have an EE degree but only pretend to be one at home, on weekends, for personal projects. I ended up in IT a few months into my first job, and been here 30+ years). I now work for a consulting firm, have for the past 20+ years (name on my paychek has changed a few times, but I haven't gone job seeking) so side work is a conflict of interest now, but back then I was working internal for a company so I figured I could make some extra money providing help for some local small businesses who might not be able to afford the big support companies in the area. I had a few jobs and made a little money, but I also had a couple of nightmares, including a lawyer (I will NEVER work for a lawyer EVER again) who not only didn't pay me, but threatened to sue me for an ancient used computer that the hard drive failed in the day after I worked on their server. I really should have just left the first night when I saw all the past due notices for their office's electric bill sitting on the accountant's desk - if they don;t pay their electric bill, what chance do I have of being paid? Sure enough.. So I would work nights and weekends, but not have a lot to show for it, as I thought I was charging a good price, more than I made at my regular job, but far less than the local IT companies charged their clients. Never again. Not going to undervalue my worth.