Congrats. My first sale also happened few weeks before, purchased for $3, sold for $350, transferred through godaddy push, buyer had made contact with me, he was CEO of the company and previously (till 2013) he had owned that domain, at first considering everything i expected $750 from him and he would have most likely if i had dragged it for few months, but since it was my first potential sale i was too eager to complete the deal hence quickly i settled it for $350.
overall it was nice to get $350 for $3. good deal for buyer too.
PS i have spent half of the money investing in new domain purchases.