However, very, very few people will buy an item for $250 that they did not plan to buy when they entered the store unless they run into an exceptional salesman. $250 is high enough that most people will have to budget for it and aren't going to buy it just because the box catches their eye on the way to the underwear aisle. But it's low enough that people who don't make video gaming the center of their lives will consider it, i.e. "mainstream."
It's all about the amount of cash you can afford to waste per month. If the purchase falls within the 'if I pay this amount this month without running a debt for next month', you can buy it on a whim. If it requires more than one month of 'money-you-can-throw-away-on-whatever', then it ceases to be an impulse buy. i suspect that there's a fair amount of interesting consumers for whom that monthly amount lies between the $250-$500 range. But if you wanted to be more precise, you could probably predict where the impulse buy range is for each person based on their spendable income brackets, and even link them to periodical bonusses to explain sales peaks.