When you're first starting out as a professional writer, it's easy to get seduced into saying yes to anything that comes along. You're in it to get experience and a portfolio started, so any job is a good job. Besides you don't know when that next job will come along.
I had this problem for a long time. Any job, big or small, I accepted and pretty soon I was overloaded with a lot of low pay work. Sure, I could make $20, but I needed to write ten 500-word articles. I either ended up spending all day and night working or focusing on the higher pay jobs and promising to pick up the other stuff later.
What ends up happening is you start getting a reputation as someone that can't hit deadlines. That's s death knell in this business. Instead, you have to learn to pick and choose what jobs you take. I am an avid gamer and have done a lot of gaming writing through the years. One day, I saw a listing for a game writer and applied.
I found out they wanted to spend $3 per in-depth article. I told them that I don't write articles of that length for less than $20 and that I would be unable to accept their offer. I'm sure they weren't happy about it, but they should pay writers what they are worth.
Never be ashamed of turning down a job because of pay. You're not there to make them happy at all costs, you're there to provide a service. If they think you're worth it, then they should pay you something comparable.