Depends on how much they own. If they have (no idea if it's the case, just illustrating the point) 75 % of the wealth of the country, then paying only 45 % means they pay much LESS than they should.
And don't forget that they should actually pay proportionally MORE than the raw share of wealth they own - because a much higher part of their money is above the treshold for living - someone who earn 1000 bucks and need 800 to pay for his basic needs, has in actual disposable wealth barely 200 bucks, while someone who earn 5000 and pay even 3000 for his needs, has 2000 disposable wealth (so he has ten times more while earning only five times more, and that's with being generous and considering he has "basic needs" nearly four times more expensive).