*On the stuff with a market. I'm not sure what Doge has done; but payment processing is the hardest part of a retail store utilizing any crypto. Any store that uses BTC goes via coinbase, not an exchange. We may first need a licensed payment processor.
On this one, I'm trying to think it through. There may be a way to achieve payments without being a payment processor, and instead serving as an escrow agent, especially if the store is more of a "middleman". I'd be curious to hear what others think. If instituted this way, then price is determined at time of sale. I need to really think about it and draw something up. A lot depends on the kind of store - to be a retail store like dogestore, you would have to interact with suppliers. But if it were more of a "user sells his stuff" store, performing escrow might work well, as no fiat would ever have to be exchanged.
Yes, without a processor, some middleman (store front) will front the risk of any purchases. For product acquisition, that could be tougher; depending on the method. Any electronics, generally require quarterly purchasing agreements to get any price breaks. Larger corporations or distributors of products look for similar requirements.
However, there may be products purchasable in smaller quantities via foreign sources or ebay (heh). Also, as was mentioned (I believe by halofire). Purchases could be done on a "per order" basis; but again, may induce higher risk to the merchant.
Coinpayments.net create a checkout system that's easily intergratable. In the last round of votes to get added we only got 2. But next month we should all vote everyday so they create a ultracoin checkout system
Ye I saw we missed the voting for that.

Edit:
Gold is a store of wealth, you are saying crypto is more like gold as a commodity than as a currency. ...... -snip-
Yes I'm one of those that believes crypto has more of a commodity future. Even with stores, BTC still fits more of this definition. But I do think, if crypto succeeds; that there will be more currency types.