This undated photo provided June 1, 2012, by Target Corp. shows one of the T-shirts target is selling to raise money for a group working to defeat a gay marriage ban in Minnesota. The Minneapolis-based retailer is taking heat from same-sex marriage opponents in its home state, where voters will decide this November whether to put a gay marriage ban into the state constitution. (AP Photo/Target Corp., Paul Weber) Associated press file photo Online prices for everything from food processors to flat-screen TVs can fluctuate by hundreds of dollars, from site to site, day to day, or even hour to hour.