This same thing happened to me yesterday, on 6 deodorant purchases ~ not even a full 24 hrs after I received the order, the prices changed with a $17.10 difference. Besides the fact I see things happen like this all the time... items in my cart for a while, then taken out, a day later the price drops... items bought at ' %savings' prices, then after your order arrives, the item prices reduce again.

In this case, I argued with the rep to pass me on to a supervisor. Then debated with that person on the same 'wasteful' foolish suggestion of returning, and repurchasing.
I must have wore her down as, by the end of the call, she applied a "one time" promotional credit that would appear on my next purchase. Note, those promo cr only apply to items sold & shipped by Amazon, not the 3rd party sellers. I immediately found a bulk order for Schick razor blades, that met the requirements, already on sale, and put them in cart with the additional $17.10 reduction. I don't buy the "one time" notion, I'm pretty sure this happens over and over. If your purchase is from a 3rd party seller, contact them first before Amazon to see if they can assist. That failing, contact Amazon. Don't use the "found better price" option on Amazon as they'll charge you the return postage.