wow, thank you for doing the math.
devil's advocate is much appreciated.
see the image above, it was shot at 118mm (converted to FF AOV), something the 24-70 won't be able to do
6 months to pay on the 15-85!
The 24-70 F4L IS has macro mode and can focus a lot closer than the above. It can focus at 0.7 feet at 70mm with 0.70x magnification.
By comparison, the 18-135 STM has a minimum focus distance of 1.28 feet and 0.28x magnification.