I didn't bother with the $50 survey, cause if I did get the $50, it would probably be in the form of a check, which would cost me $30 to cash, only leaving me with $20 (giving the bank the higher percentage), so I don't see it as "economical" for me.
$75 would only bring me $45, which isn't bad, only cause the bank doesn't take the larger percentage, anymore...sorry I couldn't help you there.