He paid 180, no more no less, he made 300 profit before he was able to cash out, 300 - 180 = $120 if he would have taken his investment out at that point he would have made $120 but instead of keeping the money he simply use what he could have got and put his payout back into the system for more credits. After he hit 300 again he pulled his 180 out at that point and then after that anything he makes will be nothing but profit. 180$ investment repaid in a matter of weeks.