Benefit cap has been reduced to £23k too (if you're in London - £20k outside of London). Those figures are a lot lower than your starting point of £28k.
I've posted this/similar before, but approx 49% of the total welfare bill goes on the over 60's. If you genuinely wanted to make efficiency savings that make a difference, that's where you'd go. No government does, because all party's are worried about the impact of such a policy on the "grey vote".
The next largest proportion of welfare is approx 36% on tax credits.
Over 80% of housing benefits claimants are in employment.
Fraud accounts for less loss in the welfare system than official error.
The total JSA bill is miniscule. Here's a pic, look how tiny the JSA segment is:
The cuts to welfare are miniscule in the grand scheme. As such, the so-called "logic" of it being to bring down the total spend is erroneous. The cuts implemented, are therefore ideological.