I would buy myself one of these, if the iso would top at 12000 not 3600 and it would deliver 4k image, not 1080p. Also the dynamic range is quite bad here...
sigma 18-35 f1.8 delivers astonishing results, get rokinon 50mm and 85 mm + metabones speedbooster and you are good to go- sometimes it's good to have tokina 11-16 and Canon 70-200 f 2.8 , but you can rent them on special occasions.
Scenes is right, you can't now say "Okay, you know, I spoke to some professional shooters at NFS and they say I should charge you double/tripple, so let's change the agreement" because that would be a greedy solution to the situation- you could research that earlier, now it can break your relationship with the client. You may say now that she can suggest the fee if she thinks it's too low or you can rise it up a little bit and say that if they will be pleased with the product then they can pay you with an industry standard rate.
The shots are really great, thanks for posting your work ;)