You get about £61 a week to care for a severely disabled person. That's less than job seekers and about half as much as pensions are. The amount paid in carers allowance is classed as taxable income so your tax credits are dropped. So you don't actually get the £60 even.
It's hard work caring for someone and as it is soo hard to find childcare suitable for a disabled child working is often out of the question for many parents of a child with a disability. Personally I notice people moaning about how low state pension is and how low job seekers is yet carers allowance is the lowest of all.