By the standard point buy rules you can't buy anything higher than a 15. The only way to get an 18 with this rule is to buy a 15, get a +2 racial bonus and then spend four points to get a half feat bumping that to 18. That gives an array something like 15, 14, 11, 10, 10, 8. So... one great stat, one good, three average, one bad. That's okay, really.