That's not what their website says. I'll email SB and ask. SB lists their most expensive leather, Japanese leather, as adding £200.
I’m just saying what it used to be. In any case, I wouldn’t personally ever buy something from SB, even if the jacket was £100 given that they’re unrepentant criminals who stole their patterns from Aero. But many people here are fans and customers of theirs.
If you do order from them, good luck avoiding the usual measurement nightmare.