These percentage of income estimates are catchy formulas for TV and radio spots, but are generally pretty useless. It doesn't take into account that a family making $30,000 per year would have a much harder time coming up with $450 of disposable income after all their necessary expenses than a family making $250,000/year would likely have coming up with $3750. There is a certain "minimum" most families need to live -- you can only cut housing, food, clothing so much. For families that have larger salaries, if they generally lived below their means, they could easily be very elaborate with their holidays without causing any financial hardship for themselves, while a family barely making ends meet couldn't dream of spending 1.5% of their income.
Black and white financial advice makes good TV but lousy policy in a grey world.