Thing is, we use both systems now. What huge cost is involved by saying "Starting in 2020, the metric system will be the official unit of measurement in the US.

Thing is, we use both systems now. What huge cost is involved by saying "Starting in 2020, the metric system will be the official unit of measurement in the US." Manufacturing companies can switch as soon as they want to. Most consumers' toolsets already have both systems (wrenches, sockets, etc).