Pixar Short Films Collection Volumes 1 & 2 (region-free blu-rays) $17.18 after shipping from Amazon UK
Volume 2 specifically says "region-free." Volume 1 shows region A, B, & C on the back cover picture, which means it's region-free since there are only three regions.
The price of each set drops to £4.16 after removing the VAT for shipping to the USA. Shipping is £4.07. You can save a small amount if you pay in British pounds with a credit card that doesn't charge for foreign currency conversion, such as Capital One.
Each set is $19.99 on Amazon.com currently. The only advantage I can tell of the American versions is they contain a DVD copy.