If you were married, I can see where she is going with this, but if you just started seeing each other, then she's way overreacting to this. I would say just ease her into it and let her know this is you and who you are. A few girls I dated in the past didn't accept my collection and said I had to grow up, needless to say I'm no longer with them, the current girl I'm with accepts me for who I am regardless of what collectibles I have in my room, I'm also financially stable so money is never an issue. She laughed at first when she saw my room and said it was "cute", but she would never get into this stuff, a year down the road, she's going to comic cons with me and collecting figures herself, so it really depends on the person also, sometimes you may think the person is right for you, but as time passes by, you will realize if you're really compatible. Give it time and if she's really serious about you, then she will accept you and your collection, if she doesn't, but you still want to be with her, then just narrow down the collection and make select buys just to show her it's under control, but a person can never change who you are. When you're married and have a kid along the way, everything I just said goes out the window, you will be willing to give it up for your child. Just take it slow and see where it gets you. I know a lot of collectors on here who are happily married with children and their spouses accept their collection (they may limit the size of growth), but they still accept it. Best of luck to you.
You can't just tell them the full retail like that. You gotta be vague
tell them: I got a great deal/I never pay retail/I have a supplier/It was a trade/I had a coupon/I sold some stuff to cover it, so it was basically free/I paid a year in advance so I can't remember a specific number/This is a custom I made from spare parts/I won a contest/Thats an old one I never opened before/Well because of the fluctuating Euro -and Greece, you know, who knows/I actually forgot I ordered this, it just showed up one day/Hey remember that cat we have? Where is it, I think it got out!/We should get a cat/Who could put a price on emotional stability
My wife is indifferent about my collection since she just can't get used to the fact that each piece is $200-350+, but hey, all the bills are paid, we go on trips often, and we're not eating ramen every night so she really has no say 
This is why I love the Marvel figures board 
