A consumption tax still needs to be combined with other things. We already have luxury taxes and it just doesn't matter. The amount of wealth generated at the top is unfathomable to the point where dollars don't matter, they have no value, and frankly those people are probably burdened by the concept. They don't look at numbers and the probably don't even know how much their numbers person gets paid because it doesn't matter.
A flat rate consumption tax would be a total reversal in terms of buying power because it's not even possible for the market to offer most products at a price and thus taxable amount that effects these rich people in the same way it effects everybody else. If I pay $300 for a perfectly effective television, a television for a billionaire hundred-millionaire would have to cost $300,000. A billionaire would have to pay $3,000,000 for a TV to be proportional. That doesn't make sense and even if it did nobody would buy it because the $300 TV already does everything and lasts for years.
Money doesn't exist to these people because the vast majority of products don't have proportional costs. If I pay $5 for a loaf of bread they might pay $10 at a fancy bakery...but the proportional cost would be $5,000. I invite you to find me a $5,000 loaf of bread so that rich people can pay a proportional amount of sales/consumption tax.
The only way a sales tax makes sense in terms of proportionality is if the sales tax for a product is calculate based on means at the point of sale.