Depends on the friend. We are friends (not close, more cordial acquaintances) with a couple who literally think nothing of dropping 1,000 quid going out for dinner on a Tuesday night because they can't be bothered to cook (they like their very, very good wine. And their coke, it has to be said ). But they're just as happy to bring sausages to a BBQ, so that's how we socialise with them.
On the other hand, my friend who has an unbelievably high-flying job dresses like the earth-mother hippie she is and socialises at the rather grubby local pub. I'd actually known her for quite some time before I realised she was absolutely loaded.
Sometimes people honestly don't realise. When I first started going out with my now-husband, he was earning quite a bit more than me and I had to have an embarrassing chat to get us back onto the same financial page. We were going out for dinner three times a week and splitting the bills (my choice), and he really had no idea that I was having trouble keeping up and that we needed to start going to cheaper places.