Someone on £20k isn't even doing a full time minimum wage job - yet will still be topped up to cover their housing, and extra to live on to a more than acceptable standard. Not just the basics at all. As well as free money, they get cheaper bills (social tarifs), reduced council tax, free prescriptions and opticians, and even reduced attractions entrance as we learned recently! As well as free access to state provided services - free medical care, education etc - which cost the state an average of £10k per person each year.
Sure, they'll be paying £2k tax per year. (assuming you meant they actually earned the £20k. If the £20k was benefits, they're paying nada). It comes nowhere near covering even the services they get, let alone the handouts.
Whereas someone on £200k is handing over £82k tax. And not getting any of those tax discounts or free extras.
How the hell can you suggest that they're paying "the same rate of tax" ? 
The £20k earner is a net recipient - paid for by absolutely huge amounts of redistribution from the £200k earner.
You're right that it's not fair. And you'll only realise how greedy you are when it's too late - when you've pushed it too far, and those high earners have stopped massively subsidising you.