10X of the poverty line might be gravy, but higher taxes at that level might also be a disinsentive to produce more wealth - and more jobs.
Why 10X the poverty line, why don't we just tax everything above the poverty line since that is the place that you can survive?
Taxes on income punish a person for producing (earning) no matter the level. Have you ever seen the articles that show a family of 4 earning roughly $20K actually has more disposable income than a family earning $50K? It takes a considerable amount of money (percentage wise) to go from welfare to taxpayer - so much so, that it isn't always worth the effort.