Monstrous Mondays: How Much for a Book?

I had a Monstrous Monday planned for today but in the process of going through my monsters to make sure I hadn't already done it (spoiler: I hadn't, expect to see a Hodag soon!) I began to notice a couple of things.

1. I have been doing Monstrous Mondays for a while now.
2. I have a ton of monsters.

I went back through all my data and found I have done 230 monsters for my witch books.  About 80 for Monstrous Mondays and another 75 or so in just A to Z posts.

Counting for duplicates and overlaps that gives me over 300 monsters.

That's more than the Monster Manual had.

It got me thinking. Would a new monster book be fun to do?

Well, the answer is yes, it would be fun. I have enough monsters for sure.  They all have a general "theme" of witches, demons, undead, and the occult.  So that is something.

The biggest issues are:

1. Art. Art is not cheap and I would like to have as much as possible.  The biggest cost of the book will be this.

2. System. As of now I have written monsters for Basic-era (at least four different clones), S&W, AD&D, Unisystem, AGE, Ubiquity, and D&D5 with a smattering of others.  What system would be best to use?  AD&D/OSRIC gives me more detail, Basic/LL & S&W gives me the most audience. D&D5 gives me a little of both, but the art requirements are much higher.

3. New content. This is a big one for me really.  Despite the fact that there are over 300 monsters, all of them have appeared in one of my books or blog already. While an individual may find something they have not seen before, anyone who has purchased a book from me will see something they have already seen.

Granted, this is the exact same thing as the Fiend Folio with content from the Fiend Factory and most of the Tome of Horrors books are filled with monsters we have all already seen. In fact there is a group of demons I have taken to calling "The Usual Suspects" because they are in every book of demons there is.  I have even gone as far as to look into commissioning some art with them all in a police lineup.

Even Monsters of Mayhem #1, a book I rather enjoy, is made up completely of monsters from all the adventures from Dark wizard Games.

Obviously, I could do this as a book and sell it anyway. The enjoyment would be for me to have my very own book of monsters.  If other people enjoy it, then fantastic!
BUT that assumes that I either have all the art I need and any I need to buy will be cheap. 
I like my witch books to make a profit (so I can buy more books!) and just breaking even is not a good business strategy.

Under any circumstance, I would HAVE to include new, never before seen monsters.

Now just figure out which ones make the cut and where some gaps might be.