Couple examples: Beale's Commentary on Revelation at Logos - $85; Amazon.com - $50.40
Word Commentaries average $40 each at Logos and can get for $25 or $30 in print.

I know a lot of stuff at Logos is cheap if you buy the whole set, but I usually don't want and can't afford a whole set of commentaries or other works. I'm usually looking for some specific book.
Also, their public domain works are often much more - like works of Pink or Owen or Spurgeon. I find Ages cheaper for a lot of those Classic works. I'm not sure if it's the technology or what.

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Mike Shingler
Pastor: Steep Hollow Baptist Church (SBC)
Bryan, TX