If I build a box and sell it to you, the cost of the parts is cogs. If you buy someone else's box through my website that's gmv. Your example is correct too, bu

If I build a box and sell it to you, the cost of the parts is cogs. If you buy someone else's box through my website that's gmv. Your example is correct too, but probably not what somebody would use because in that example it's also the revenue.