So far i have been sending $250-$300 per month as per my parents expense. They are happy and satisfied with that amount of money and never demanded anymore. I think parents understands the value of money better than us and so they do take care of every penny we send. Beside that i send couple of thousands in any special occasions. Sending about $200-$300 a month to parents wont and doesnt hurt your retirement plan or whatever plan you have. We tend to spend $5-$10 on a cup of starbucks or cigarettes or something else.. And afterall they are responsible for what I am today and it gives me pleasure if they are happy and satisfied no matter it comes at cost of spending extra few hundred dollars a month.