I didn't get to choose. I felt desperate at the time and took flat rates for jobs that seemed fair, only to find that the requirements kept shifting. The client would refuse to pay unless I did more work. It ended up being like $5/hr in the end. Like I said I felt desperate and needed rent money. It sucked.
Another time I'd put all this work into bidding for a job only to find out they didn't really have any money for the project and were just using the conversation to get feedback on their idea.
It varied. I got my first programming job on Upwork (React Native), and it was around $3/hr. At the time, it felt magical earning something from the internet, and I was in college at the time. $3 was the amount I spent a day. It went sideways due to various things. Then I did a couple of tasks for a fixed priced and then went on to a React job for $18/hr. Most of my jobs have been around $20/hr, which is wonderful where I live. I tried raising, but good luck with that when it shows you're not in a developed country. But the major burden was the tracking. After, there were the shifty clients, the client that won't communicate with you, and the ones that consider you as a serf.
Now I've got the work experience and the savings to be really picky about work. So, I can take my sweet time to consider posting, if I ever go back to Upwork.