Earning from Adsense depends on number of factors including the Cost-per-Click (CPC) and Click-through-Rate (CTR). If you have content based on high CPC keywords and get traffic from western countries, you can make a decent earning.
For example, if you serve 10,000 page impressions per month with average CPC of $0.50 and a CTR of 3%, your monthly earning could be $150.