How do you guys know how much to ask for freelance work? I'm always scared to ask too much and lose a client

I used to freelance on fiverr. First couple jobs I did for $5 just to get a rating.

Once I had some reviews under my belt I got more and more request so I raised my rates to min $25 - $50. This helped filter better clients too.

I'll be honest, I took on some jobs I didn't fully know how to complete at first. I learnt a lot while working on them. Then when it would come up again I'd be quicker at resolving the issues.

I often worried that if I finished the job quickly they would feel like they overpaid, but, it's the opposite. They are happy for a quick resolution from an expert and willing to pay for more help.

I've had customers tell me horror stories from cheap devs that would disappear and never complete the job. So don't worry about others undercutting your price.

I'd recommend charging what you feel your time is worth. If you charge too little you'll get cheap customers that will demand the world from you.