It takes Benji a few moments to figure out what Emma is trying to signal to him and then a few more to realize, with poorly-concealed alarm, that the whole reason Emma brought him along was probably to facilitate this transaction. Any member of London’s supernatural community would recognise Elliot’s name and authority, and trust that Benji wouldn’t be stupid enough to leverage that without Elliot’s permission, but this doesn’t seem like that sort of place.
Not wanting to embarrass or disappoint Emma, Benji begins rummaging through his pockets as he frantically tries to figure out a solution. "Oh! Um… Of course. Let’s see…"
He came straight from the train station so he is still carrying his earnings from this morning, --mostly in the form of coins and £5 notes-- but he suspects he doesn’t have nearly enough to cover the cost of the dress, let alone the shoes too. "Oh dear, I, uh… I must have left my money in the car. Wait here. I’ll be right back."
He sprints out of the store and returns a few minutes later with an old shoe box (circa 1920, if one had to guess), having retrieved it from his lair under Piccadilly Circus Station. He sets it down on the counter, brushes off the dust and cobwebs, and opens the lid. Inside, there are a lot of pre-decimal coins and bank notes that are no longer legal tender, a dead mouse, and a few definitively not-dead spiders, but among all that, there is enough actual money to pay for the dress and the shoes – 200 years worth of savings. "And that mouse is worth a few pence too, at least, if you ask me," Benji adds, hastily recapturing the spiders before they can get squashed and putting them in his pockets.