"No matter how rich, it's unthinkable to spend so much on a meal for us; after all, with so many of us, it would easily cost... hundreds of thousands."
Their group was large, and they ate a lot, so an estimate in the hundreds of thousands seemed about right.
But spending hundreds of thousands to treat these volunteers to a meal was considered impossible by anyone.
Upon hearing this, those looking forward to it also calmed down, "Right, it's too expensive, impossible."
"Eating here once probably costs more than making a donation, so just forget about it."
"It certainly won't happen. What we're doing isn't charity; it would just be a dinner party."