Yes, you cant be more right about 90% interview invitations being spam. Sometimes I wish there were a way to send a message to the client when they fix a budget to $5 for a script and $75 for a SDK. but the thing is once you have done few projects on Odesk, its easy to get more. for eg, the Diffbot client invited me to write python sdk even though I dint apply for the project and I think that was because of review left by my previous clients. and take a suggestion, dont take small projects like fixing js code, fixing server bug which yield 20-30$, have patience and try for something worthy of your time.