If you scan a B&W text page at 600 dpi into Adobe Acrobat, and apply fax-style run length compression you'll get a file of about 60K.
Use OS X to create the PDF and the size will be 2MB.
The difference is compression choice. Lossless run-length compression works very well for B&W, OS X is probably using JPEG or TIFF.
What you want are better ways to control PDF size in OS X. The default "Reduce Filesize" quartz filter is lousy, but this page tells you how to create your own filters: Shrinking and Compressing PDF's - Yeraze's Domain.
The trick is to use the ColorSync utility.
I'll have to see if I can create a good one for B&W text ...