As a parent of a high functioning ASD child, without any disability benefits I hope I can enlighten you on your query.
I was a higher rate tax payer in a very good job but had consistent problems with my elder sons behaviour. The stress of his challenging behaviour was a contributary factor in his father leaving, child carers and play groups not being able to cope with him and then when he started part time school being phoned and called in several times a week, when he was regularly sent home. As a single parent of then 1 and 3 year olds I reduced my working hours (for my own business) to part time and we lived below the poverty line because ironically I kept working.
School assessed him as ADHD which didn't fit with my findings at home but with the help of two educational psychiatrists, physio, occupational therapy, speech and language therapy, three GPs, two community paediatricians, a community psyciatrist, an emotional play specialist and now the CAMHS unit we are finally getting a full assessment report as ASD which means we can get him statemented to finally get some support for him. Its taken three and a half years of several days a week, no support (I have another child) and a forced change of schools. At the stage we changed schools and had to sell our house I stopped work. Very fortunately I've met and married a wonderful man who has taken on board our challenging family and enables me to commit the support needed to bring an element of harmony to family life.
My DS is unable to attend after school clubs, some day time school activities, child care, or be picked up by other mums as a favour because his behaviour is not yet in the normal range. Its a one hour drive to the hospital where we go a couple of times a week to see specialists. Our life routine needs to be strict so that he doesn't freak out and do damage to himself and others. Support available whilst we get a lot of specialist advise is not able to develop him to be a contributory part of society so self education is critical. Reading up on management techniques and reviewing his weekly needs with the school again takes time.
At the end of a school day we need to review the day and discuss how to handle each emotional incident, do physio and occupational therapy exercises, get him through a plate of food (around an hour) and very carefully handle washing and teeth brushing which are very distressing and take up to an hour. We then need to very carefully handle his bedtime routine because changes in this can result in no sleep which makes the next day even more challenging.
The costs involved are losing my life (working and social) and having to give up my well paid job and pension, travel to hospital and specialists, buying specialist materials for occupational therapy and physio, extra childcare for second child, buying educational materials to enable him to develop potentially to operate within societies norms. Even if we had the money things like holidays and days out are not an option because they represent a change in routine that can cause major stress.
I have every confidence that with ongoing input he will be a higher rate tax payer, his IQ is through the roof. He just needs a lot of input to learn to interpret emotions and non rational responses and language. ASD is not curable but is in part 'treatable' with the right input and support. However parental support is very draining and isolating.
If you have children do you remember that phase of being exhausted at 3 in the morning and for no reason what so ever your little angel wont stop screaming the house down?
ASD can be like this, every day. Because the brain works in a foreign way understanding the distress of the child and helping them work through it/ find a way out of it is challenging. Add to the screaming abusive ranting and quick fire rounds of complex questioning and you're soon beyond exhausted.
I've no doubt what ever benefits system we have a minority of people will find fiddles however just because you can't see ASD it doesn't mean that the practical and physical support needs aren't their.