Theres a lot of folk with zero idea how much work a cake like that actually is.
Make and stack 6 cakes - so that means ensuring they're all the same size and level, and probably some sort of support inside so nothing slides off sideways.
Crumb coat with buttercream.
Outer buttercream layer.
Drippy poured top of whatever that is (chocolate? ganache? no idea)..
That alone without further decoration is a fair chunk of work and ingredients and probably minimum £50.
Then add all the other stuff, some of which is handmade chocolate work I think, so thats probably another £30-£40.
I would at the very least, cover cost of ingredients and a couple of hours if you want to give a mate a discount.
To sell it properly, double or triple the cost of your ingredients/overheads to come up with a profit making charge.
I think it looks very good, professional quality nearly... and I say nearly because theres a lot of bits on there that will go stale very fast, within a few hours, so you'd normally add very few of those and only put them on at the last minute before the cake is to be revealed/served (which is only practical for cakes you're taking to a venue and setting up there for weddings or big birthdays, not for cakes someone will take home and serve later or the next day).