You'll pay extra for absolutely everything at LCdH, but the upside is that you can be as sure as you are going to get that you are receiving what you are paying for. Where was this LCdH? Keep taxes/VAT in mind, as well. As for "aged in house", some places will consider it a premium service, while other places will just consider it luck that you ended up with a 5-year-old box. I've heard people say that LCdH, as a rule, puts boxes away for several years before selling them with an upcharge -- though that is certainly not a blanket statement. Keep in mind that LCdH is a "franchise business", if you will, so each store sets their own policy in that regard. My local here in The Hague sells them as they get them in.
Without knowing anything further than what you've told us, my take is that she paid more than would elsewhere, for sure, but it's not out of line for LCdH -- especially if it is coming from an area with high VAT.