These files are the same size!
JPEG 2000 compresses images with less objectionable artifacts than regular JPEG.
Download the original source file and compare.
(The JPEG 2000 file is displayed here in PNG format to avoid further re-compression.)
This file saved using highest JPEG compression setting (smallest file size) in Photoshop.
Notice the 8x8 pixel artifacts everywhere.
Notice it gets especially bad around the text.
Also known as:
This image saved by specifying a 16k jp2 file.
But wait, there's more!
JPEG 2000 also supports advanced features such as a lossless compression mode, alpha channels, 16-bit color and more!