That's flat, not progressive. Progressive consumption tax would mean that the first $5.000 worth of goods you buy are not taxed, the next $15.000 are taxed at 1

That's flat, not progressive. Progressive consumption tax would mean that the first $5.000 worth of goods you buy are not taxed, the next $15.000 are taxed at 15%, everything beyond that at 20%. How will each vendor know which rate to tax you at?