Billhelm: JPEG compression is variable depending upon the content of the scene -- lots of plain, blue sky, for example, will compress more than a sky filled with clouds and birds. A desert or ocean scene will compress more than a complex forest or cityscape. Hence, different images will end up different sizes even though they all may be compressed as "4" on the relative jpeg scale often offered when saving the final file.

Bear in mind, too, that jpeg is very lossy and a file that is saved a few times will quickly begin to show the effects of deteriorating quality. Make your edits or size changes and save your files under a new file name as a *.jpg only one time. Keep the original file on your system as either a TIFF or, if you can, as a raw image file.