The $50,800/gram figure seems to be based on the total cost of the entire Apollo project - $50,800 * 382 kilograms of material returned = $19,405,600,000, which

The $50,800/gram figure seems to be based on the total cost of the entire Apollo project - $50,800 * 382 kilograms of material returned = $19,405,600,000, which is about 4/5 of the total Apollo programme cost listed on Wikipedia. That seems a little unrealistic to me, because the goal of Apollo was not "bring 382 kilograms of moon rocks back at the lowest possible cost", or anything close to it. Obviously there are some big hurdles to overcome, but I don't think they're as enormous as "reduce cost by a factor of well over 1,000".