I think its just from their experience as customers elsewhere.<p>For me — $10 for a simple service seems a little pricey, $9 is basically $10 still, $8 is still a a tiny bit high — but $7 is the sweet spot! Same goes for higher prices too — I like $37 rather than $40. I'd think less about paying $17 for a service than $20, $19 or even $15!<p>Not sure why, maybe its because the $7 on the end becomes my focus:- its still technically pocket change — but also in the higher end out of 10...and I think about it more than the $30?<p>(plus if your picking smart numbers for prices, check out the "common" exchange rate people think of without checking. For me, I think of a dollar being worth £0.50p, so $37 is around £18.50, when in fact its over £21; for some it may not make a difference, but for others, the extra few pounds to nudge it over £20 may be enough for them to pick a slightly cheaper plan. And I would imagine a similar thing happens with the euro and other popular currencies also.)