The benefits cap isn't all it's cracked up to be. That £26,000 number is an average income, not the minimum, so by definition a great many employed people are earning incomes below the cap. If you assume that many benefits claimants would be entering the job market at the lower end of the pay scale, there's still less incentive for them to work than the Tories are saying.
Anyway, I think the issue is less about what benefits are like when one starts claiming, and more about how long they run for.
Update: interesting discussion (as always) at Marginal Revolution. Many people point out that the real biggie is accomodation. This Guardian article deals with the same issue. I think how one feels about the plight of the woman in the article depends a great deal on how far away one has to live from central London and how far one has to commute to work every day. Her situation is awful for her but there's no getting away from the fact that spending public funds to preserve her lifestyle is by no means fair to the nameless and faceless working taxpayers who have to fund it.