I reviewed an oreilly book. The process was well run, and most of my suggestions were acted upon by the editors/authors. Everyone was quite professional.

Compensation was de minmus, plus a copy of the book.

I strongly suspect that tech books do not sell as well as they did 25 years ago, and most tech books make little if any profit. There's an advantage to the publisher in having a wide variety of titles for a subscription service (I loved having a safari subscription), but, at least for me, the days of buying a giant and expensive tech book for just a few relevant chapters are over.

So the addressible market is smaller, and compensation is generally lower, though there are still indirect rewards