Where I lived, it was predominantly 3 bedroom houses (2 and a boxroom); with large families, that is not extravagant. Expensive looking clothes - in what way? Most people I know are not buying expensive; when I was in the UK, I shopped in primark, george, next, supermarkets mainly - what area were you looking at? It could have been an affluent area, but most Jews are not wealthy.
Jews give a minimum of 10% of income to charity, so ambulances are fundraised for. They are staffed by unpaid volunteers (trained). The men do earn money, and in many (most?) families both spouses work. The men who learn while the women support them is predominantly in Israel, or with young couples who get family support. There is a lot of community giving, fund raising, and free support. If I was making an event, I could find a gemach (free lending/help organisation), for anything from extra freezers/fridges to borrow, to people to volunteer to set out my kiddush (um, event? don't know translation), to tablecloths (often only pay a refundable deposit, and cleaning), centerpieces, there are multiple ones for wedding dresses, veil, headpiece, or gown for an event... There are gemachs for medical equipment, lifts to hospital, baby cots... you name it someone wants to help. So we pool resources a lot.
If they were struggling, yes they would claim benefits.