It's more about the difference in stats than the stats themselves. It's no fun having players with 18's and 17's, while others are running around with 13's. 13's on themselves are not the problem.

Also don't link Combi's comment to my stats directly. It's her decision, not mine (I personally wouldn't make such a drastic change after starting).

Anyhow, if Combi insists on using pointbuy, it works like this. You have a certain number of points (Combi seemed to go for low-powered so 22 points total). You use those 22 points to buy 6 scores, and assign each score to one ability stat of your choice. Apply racial modifiers afterwards.

Score 8 costs 0 points.

Score 9 costs 1 point.

Score 10 costs 2 points.

Score 11 costs 3 points.

Score 12 costs 4 points.

Score 13 costs 5 points.

Score 14 costs 6 points. (So up to here it's reasonably cheap)

Score 15 costs 8 points.

Score 16 costs 10 points.

Score 17 costs 13 points.

Score 18 costs 16 points.