I do not know about the economics of inspecting, steam cleaning and reusing Coke bottles – that is not the objective.
We stop use plastic bottles clogging up land fill and the country side – killing wildlife, and making the Earth a tip. They charge a deposit in Germany – and presumably France, where they value a clean environment.
So we get the bottles back – even if we just sell them on for repurposing – as shipping pallets etc..
Pepsi and Coke can improve our world – and that PR you can't buy.