It sounds like something that would be done by a friend I had (not a friend anymore)!
I think it's a crass behaviour, probably out of jealousy because she's making everything between you and her a competition and keeping score. I'm guessing she told you the price in your face because it isn't really very pricey? Like she wanna tell you your DH isn't really buying something very lavish for you to make you feel inferior and tell you there is nothing you can brag about (because everything you say, she thinks you're bragging, even though she asked you about it first)
Just my guess, because that's what my "friend" always did back then. She paid unnecessary close attention to everything I said, I owned, the way I lived, the jobs I did, even the way I wore my makeup and styled my hair etc... And she likes to comment in my face. Sometimes it's like, "oh, look at you...", like she's complimenting but they're all backhanded compliments to make you question whether you deserve to have nice things /achievements in life, because she didn't think I deserve anything as long as she didn't have the same things if not better.
If your friend is like mine, I can picture she likes to pretend like casually asking something about you that may sound weird to ask, because in her mind she already plotted about how to drag you down with those information. In this case it's your birthday gift, in my case it was something like "does your DH buy or rent the apartment?", and when I told her he bought it she asked "do you help to pay the mortgage?", and when I said no, she started to keep saying things like "oh look at you, I want to be provided by a man like you. You're so lucky you don't need to work, don't need to pay rent...", but I do work as a freelancer and self sufficient, it's just she kept ignoring the fact and implying that I didn't earn money or anything that I had, to make me feel like I didn't deserve any of the things that I owned and the kind of life I was living.
This is the way they extract information from you, pretend like it's casual and friendly conversations, and you answer their weird questions because you feel like it's rude not to answer as they make it so casual and friendly, and you tell them everything out of trust thinking there is no harm disclosing something private to a real friend, except that they're not "real friends" and they would always find ways to use those information against you.
It took me 20 years to realize she's a textbook narcissist when she became more blatant and frequent in trying to drag me down and dim my light ever since I got married and living in a bigger nicer apartment than hers. She started to not only verbally insult me but also my DH, so that she could feel better about herself and hers.
This kind of "friends" who likes to compare and compete is a thief of joy. Perhaps your friend is not as extreme as mine, and perhaps like some people here think what she did was totally normal...? But I experienced it firsthand and it almost destroyed me... so just here to warn you that a little red flag like this today may be a sign that she's someone you may want to keep away from.