Do you live somewhere where $30/hr is a good wage? In the US, a decent iOS freelancer should be getting at least $100/hr -- you can't do that by competing on these platforms.

The standard advice for getting better rates (you'll see all over HN -- and I can tell you that it's what I do personally)

1. Charge by the week, not by the hour.

2. Sell the business result, not the app's features.

3. Your cover letter should reference how your portfolio projects delivered (profit, cost saving, risk reduction) to the client.

4. You need to convey that you are the low risk choice -- money to you definitely turns into an app for them.