Is the place of purchase important?

I only ask, because Costco in the USA (if you are ever there) often has fantastic deals on sometimes magnificent jewels. Once went diamond shopping with my father (for my mother), ended up buying a pretty fancy solitaire that ended up being appraised for almost twice the purchase price according to the GIA certificate (Antwerp issued). They've got everything from fairly "simple" diamond rings in white gold to extravagent multi-carrot, flawless, fancy coloured diamonds for obscene amounts of money (that appraise for collosally extreme amounts).

But if the setting and place are important for the actual proposal, then never mind... a big warehouse isn't exactly romantic, buying a $20,000 ring along with an over-sized bag of trailmix.