I think Ghaz will be more like Redemptor price than Guilliman.
£40 vs £37.50 is not a big difference. The bottom line is that 60:40 is a reasonable price split for the box based on the RRP of the units inside. And if you can't find a buddy to agree then eBay will likely be full of box splitters.
Sanguinius stood up, stretching his wings to their full extent. He flexed his hands. "I need no blade".
It was as though Sanguinius gleamed with pale light, his face white, eyes becoming blood-red, surrounded by the golden crown of flowing hair. Guilliman had witnessed glimpses of of his brother's wrath before, but had never seen the true Blood Angel unleashed. Sanguinius surged forward on alabaster wings, half a meter from the floor, whiteness streaming from him like flames.