so lets say the onednd monster manual is $40 on dnd beyond. That gets you the statblocks and art. How much do you think the vtt models will cost on top of that? There’s a likely price point in between $0 and hundreds of $
Zero.
Why would you think that they would sell you a book that you cannot use? Since you are using the book with the VTT, and buying the book to use with the VTT, then that book will have to come with models to use with the VTT. If the book is 100 dollars (book+models), no one will buy it. Why would they?
Now, again, I wouldn't expect multiple models in multiple poses for the basic Monster Manual book. That would be unreasonable. But, you are certainly going to get one model per monster. Otherwise, the Monster Manual doesn't actually function in the VTT.
The money is in the subscription, not the book sale. The book sale is just icing. It's that monthly sub that you and your five players pay that is going to be where the big money is. But selling a Monster Manual without models is pointless and there's no way they'll be able to sell the Monster Manual for more than the print version. They'd get crucified if they tried it.
The biggest question in my mind is whether or not you will have separate books - one for D&D Beyond and one for the VTT. But, honestly? I doubt it. Far easier to bundle it all together. The model cost is a fixed cost. Once you've built the models for the Monster Manual, every single user that buys a VTT Monster Manual is going to contribute to paying off that fixed cost.
Sure, they will certainly sell premium models. No doubt in my mind about that. I would totally expect that. No different than the Beadles and Grimm stuff they sell right now for tabletop. But, when you buy whatever book from the D&D Beyond, you can almost guarantee that it will come with models and the price will be the same as a non-discounted print book.