antirez parent
The 500 - 5000 figure, which is correct, is why most folks should instead self publish via KDP. 70% royalties mean you can get 10-50k easily with an average book. If the book is a success, you can switch career to a full time author if you wish. All this with full creative freedom. Many years ago, I canceled my Redis book for a large publisher for similar reasons to the OP: too many "do it this way" requests.
In general, yeah. The hard-to-replicate benefit is professional editing, but this is something that most tech publishers skimp on. There are some "premium" outlets where you get some real attention, but the default Wiley experience is definitely not worth 70%.