We didn't raise the prices on the goods we had on hand, or on fabric that we had been able to order at last year's prices. (That would not be very nice to our customers!)
For instance: we ordered Kaufman's wonderful Holiday Flourish 4 Christmas line last December, before the maker's price increase on January 1st. The goods did not come until May. Any of our customers that ordered from us early enough to get their order filled from that first shipment, got the 2010 prices. By the time we reordered from Kaufman, they had raised the prices 75 cents / yard and then we had to pass that along.
Doing it this way does leave prices in a bit of a jumble, though, as various fabrics from the same collection will have different prices, depending on when the goods came in. Some stores might not like to have it that way, because it would tend to make customers ask why the red costs more than the blue.
In the same vein, some of the manufacturers that we buy from, raise prices on all their prints (new and old) at the same time. Others set the price for a collection, and do not change it (unless it gets reprinted). Only the new collections come out with higher prices.