It really depends on where you are at and your skill level. $20/$45 could be right in a lot of areas of the country.
But also your skill. It sounds like you are just learning the SDK. Are you highly skilled in other programming languages, and is the project for a speciallized business other programmers won't know?
If you are a beginner and looking for someone to fund your learning, then $20 may be spot on-and great for you.
I don't program for money, just fun. But in my technical field I get $1200/ month to do nothing, then $150 hour once I get called by my client. They are more than thrilled to pay me that because they know it would be much more expensive if I didn't do the work.
That's what really sets the rate. How much will the project cost to complete, and will the return on investment justify that cost? For a project that won't increase revenue by very much, you won't command a high price. If it will generate millions of dollars for your client, your rates go up appropriately.