"But I felt like they were missing the bigger picture."
I disagree. There are two things at work here, and they're not necessarily related. Money is needed as a vehicle for exchange. Its value is in whether you make enough to live in a way that satisfies you. Your friends were saying that the money they made was sufficient to that task. To take your comment, "And while I don't need a lot, the mortgage company and the loan company do dictate that I need at least X amount." It's not the mortgage company nor the loan company that determined that, unless you were made to buy a house or sign up for your student loans under duress. Those are choices you made, and to satisfy those choices you need to earn enough to keep up with those debts. Others may choose to live with less, and they'd need accordingly less, or more and they'd need to earn more money. I think this is the point of your friends' responses.
The other part is getting paid "what you're worth". Describing someone as underpaid is really a subjective thing, and can only be determined by the person being paid. For example, I earn noticeably less than others doing the same job I do, but that's a choice I made. I don't have to work excessive overtime, I'm not on call day and night, I have a short commute and I work in a small office with a delightful lack of office politics, so I accept a lot less money than Corporation X could pay me. Am I underpaid because I land well below my peers in pay scale? I don't think I am because there are a lot of things that figured into my decision beyond the paycheck.
In short, I don't think you're being materialistic, but at the same time you should recognize that money holds different levels of importance for different people, and your friends' responses reflect that truth.
"I would have replied to Jane and Barbara, "How much my friend earns does matter because she works hard and wants to be paid what she's worth according to industry standards. Coming home every day to a cold, dark, empty home because you can't afford better is very demoralizing, no matter how much your family loves you.""
My response to that would need to be wondering whether it matters to your friend, not to you. If she's happy with things as they are, then industry standards may not be part of her morale. I fully understand weber06 wanting to know her coworker's pay scale so that she can be sure she's on grade, if that's important to her. But on the other side, I'm with Jane and Barbara in that they can be happy with what they've got, even if it's not what weber06 would be happy with.