The file in question contains a huge blob (~12 MB) of textual metadata (see Extensible Metadata Platform) embedded into the file after the actual image data. It begins with
Originally Posted by joshman108
That metadata is not image data and its size does not change regardless of how you change your image. The tools that you used to resize the images carefully preserve that metadata, which is why your files never go below ~12 MB in size.
http://ns.adobe.com/xap/1.0/ <?xpacket begin= ...
Load your images into any editor and issue a "Save As..." command into some other format, like PNG. This should get rid of that metadata blob. After that you can convert your image back to JPG and resize it any way you wish. From that point on you will be able to reduce file size below 12 MB.
There are probably dedicated tools that can simplify the process of stripping that metadata from the files.