I agree that the Brides were incredibly rude.
Here, in NYC, money is a standard Wedding gift because most couples seem pretty well established before the Wedding. Still, objects are given and appreciated.
Why would couples in NYC be more likely to be established before marriage? That's not my experience.
I agree with Toots - guests should try to take the couple's cultural/geographical/etc. customs and expectations into account when deciding what to give. That doesn't mean they have to conform to it, unless of course it is something that would be considered outright offensive. But if you want to know whether your gift will seem cheap or strange, then do your research and then decide what to do.
I recently attended a Persian wedding in Israel as a last-minute add-on guest. The groom was my daughter's fiance's first cousin, and when she found out I was visiting his mother very nicely called her sister-in-law and insisted they bring me so we could all meet. Now, I live in the midwest, where wedding gifts are usually more modest than the east coast or Israel, and are often things, not cash. I felt like I was in the position of a "plus one," whom I would not expect to bring a separate gift, KWIM? But I decided to give a small gift, anyway. I knew that cash is always the gift in Israel, and I wanted to make a good first impression, but I thought that under the circumstances $50 or so would be really nice -- I mean, I would consider that a very generous gift from a "plus one" in my city. Good thing I asked an Israeli friend: he told me that anything under $100 would seem really cheap. I didn't HAVE to give that much, of course, but it was good to get the information before making my choice.
But the bride's response was absolutely unforgivable, and would have been even if the gift had been something that the giver didn't know was something truly offensive.
We keep a kosher home. Once a Thanksgiving guest brought us a big package of pork sausage as a gift. He was from Vietnam and I'm sure didn't have a clue about this. We thanked him nicely, put it aside, and the next day donated it someplace or gave it to someone.
I can only imagine what this bride said to people who didn't give the anything at all.
And, even as an advocate of same-sex marriage for over forty years, I too have to laugh at this bride citing "tradition" as her excuse for shaking down her guests.