Yes, and sometimes, unfortunately.
It never used to cause problems whilst DH and I had more disposable income i.e. we could still 'keep up' with them although it would mean spending a greater proportion of our disposable.
It is becoming a problem now we have DD as we have had to modify our lifestyle somewhat which has made things which were a bit of a squeeze before, just not justifiable anymore. They don't seem to understand, and to be honest it will probably mean we see a lot less of them.
I think tho that for us it has become a problem because a lot of our time with these particular friends was spent doing de facto extravagent things, which we all enjoyed at the time, we were young, it didn't matter, etc. so remove the ability to do that and we don't have that much else to base the friendship on IYSWIM.
I don't mean by that that we don't really like each other or anything, just that the things that we can't afford now were kind of the things that we had in common.
The male half of the couple concerned can be particularly blase about e.g. ordering really expensive wine if we go out etc.
On the other hand, my sister and BIL have waaaayyyy more money than us but I cannot conceive of that ever being a problem, and am trying to imagine if we were close friends rather than family, but still can't imagine it being a problem, as they're just not ostentatious with it.
D