Your best CMV Current Market Value resource is eBay's sold listings. The box from what I can see looks to be in pretty good shape as well - with just some edge wear at the bottom. Does the back look as good. We need to see all the edges to give a fair assessment of condition.
Sometimes you can get a higher price for an individual car but then you will probably not be able to sell all the others.
Right now those type sets are going for about $30 to $35 with free shipping. So on average $3 dollars a car.
Thanks the backs are great, I see what you mean by rough edges 😀