Dont pay any more than your share.
Tell them now they can all chip in or go without soon.
Point out how much it will cost them to buy takeaway.
15 a day times 5 days a week @ $3 each = $225
So if everyone chips in for one weeks worth of takeaways you have your budget.
If they dont fork out buy yourself an Aeropress from cuppacoffee (sponsor) and you can keep drinking nice coffeee while they contemplate their folly.