If you are estimating 10% waste for a typical running bond, the estimated waste of a herringbone pattern would be closer to 20%, and the layout is more difficult, as far as I know.

I'm doing a herringbone in our bedroom and bath and have done some research.

Yes, there is more waste but you can reduce that by turning the pattern 45 degrees to the walls. At least that's the info I've found! The tiler really needs to make sure they don't start drifting and that takes extra time.

DH and I did a herringbone with 12X24 tile in our kitchen. It was the first time for herringbone for us so there was a learning curve, you have to be much more exacting on your lay out as its not as forgiving. I did not think we had a big problem with waste; doubt that it was more than 10%.
But then again we are very "frugal" with our tile. More so than most tile setters.
I'd make sure he's done herringbone a few times...

Check with GW member enduring. She does beautiful DIY tilework. Her herringbone backsplash is one of my favorites.

We have a herringbone pattern in our mudroom, powder room, and back door hall.

It did cost more to have it installed, and I can understand why. I stopped by the house while the tilers were working, and they had laser levels set up to get the line of the tiles just right. It was actually pretty cool to see them line up each tile along a beam of red light. It looked like a fairly time consuming process.

I don't have numbers on the added cost; we just picked less expensive tile with an easier install for our upstairs bathrooms to make up for it.

I love the pattern; glad we did it.

PS - In addition to the extra work to get tiles lined up, I'm pretty sure there are many more cuts. You can see all the little triangles next to either side wall in my top picture. This also adds to the amount of waste as pal mentions above.

You can also do herringbone on the diagonal :)