I'm a 'flashaholic' and I've noticed this too, not only on GB but with several of the 'mega-stores' sites. I've seen as many as 5 different prices for what appears as the exact same flashlight! As best I can guess, some of this occurs when they place an item on sale; the newest listing reflects the sale price while the old listings remain intact with the old price because someone may buy it from there so they may make more profit. If you go to an item through sale or clearance links, you get the newest listing with the low price, but if you search the pages of the site as a category you see all the other listings with their various prices. Crazy but sometimes that category search will get you a better price than when searched for by the product name!
This might also reflect different manufacturers of the same item; with flashlights there are lots of 'clones' where it has been found that ordering from the same link at different times sometimes gets you a very different product internally although the outside is the same (or close to it)- obviously different manufacturers even though the name is the same and the listing was never updated to reflect that. Sometimes mid-production product changes aren't mentioned but are sold under the existing listing too. With multiple manufacturers of one product, the store may have different supplier prices so create different listings to reflect that even though they use just one set of pics and specs for all of them. It's a crap-shoot where you don't know what you're getting till it's in your hands.
Phil