Well I'm not a fan of the Tories (understatement) so my prejudice is declared, but I think the basic situation is that GO wanted to tell the shafted lower earners that he'd do something about the situation of fat cats in council houses. SO he told us all that those 'high earners' (quotes) on more than £30000 would have to pay market rent.
So, you have an income of £30000 - market rent.
Except that he forgot to mention that the way housing benefit is calculated is dependent on your family make up. You get allowances as listed here, but for example, each child in the household is entitled to £66.90 per week of your net income, before the taper of 65% is applied.
A wage of £33000 (gross) (£634 per week) is equivalent to around £490 net per week.
A family with 5 children would get the following allowances:
Couples allowance £114.85
Child allowance £66.9 x 5
Family premium £17.45
-
£466.80
So they have an excess of (roughly) £490-£466.80 = £23.20
65% of £23.20 = £15.08
So they must contribute (roughly) £15 per week towards their rent, but the state will pay the rest, because it is deemed that the family need the rest for living costs.
But it doesn't sound so good to say 'We'll make those high earners without high living costs pay to stay in their council houses....' and it probably hasn't occurred to them that people would realise that all they're doing is shuffling numbers. After all, housing benefit is paid by the council and rent is collected by the council.....in fact it doesn't even leave the account. It's just a number on a screen.