Amazon has The Princess & The Frog (Blu-ray +DVD) for $17.13 posted inc.
Amazon is selling a double play edition of The Princess & The Frog at $17.13 inclusive of postage. This includes both DVD and Blu-ray discs.
I compared it to a couple of the other online options and it is a little bit cheaper. At Mighty Ape it is $17, it is $18.95 at DVD Land and $17.95 at 00; all these prices do not include the postage charges.