Surprising? It's absolutely astonishing what can seemingly be claimed for legally. (I don't know personally)
If PAYE individuals could claim half as much we would all be a lot richer.
There are benefits, good ones, but the grass isn't always greener, there is a lot of risk. One of the main issues is people will not pay you on time, despite hounding them for it, I've always managed to get paid every invoice up to now but I've had them outstanding at 12 months before now (that is rare though) but people/companies trying it on is very common you are often at the mercy of their accounts department. I live well within my means but I was close to being kicked out of my then rented accommodation a couple of years into being self employed due to a down turn in work.
After some great and successful years I became ill in autumn 2016 which meant I can no longer work the way I used to, I had to completely change the way I work and in part what I do... while I couldn't work there was no cover/sickpay for that. The total cost of that has been huge. Luckily I have a very understanding better half and through her support we/I have survived and am trying to get back to making a reasonable living from self employment.
Self employment is hard and you have to put in a lot of work to succeed (unless you hit it lucky) so the perks/benefits you can gain are often well earned.