> If Coca-Cola manages to reduce their bottling costsIf glass reduces costs the market would likely go in that direction quickly, but we already agreed that glass is more expensive, hence primarily why plastic is preferred by the consumer. They don't actually care how the liquid arrives, they just want it cheaply and conveniently.
But let's say, hypothetically speaking, that Coca-Cola wanted to pretend to be more environmentally friendly and started making glass bottles more accessible, but also kept plastic bottles around to satisfy the actual customer demand. What reason is there for us to believe that Coca-Cola would simply eat the cost of glass bottles rather than pass that added cost onto consumers? It's not going to happen. At best you might see a short-term loss leader-type offer as a marketing stunt, but soon glass will cost more.
I mean, you suggest yourself that they will put profitability at the forefront of their decision making, profitability that is driven directly by consumer demand, so there is a contradiction here to think that plastic won't be sold for comparatively less. Glass costs more and they will, without question, pass that added cost on. Coca-Cola exists to serve the customer, not to give away things for free.
I do, indeed, assume that the added cost of glass will be passed onto the consumer because, well, why wouldn't it be? Coca-Cola isn't a charity and the price conscious consumer will just buy the lower cost plastic bottle anyway, so there is no risk to their market by charging more for the luxury of glass. In fact, it would only serve to harm Coca-Cola and its shareholders if they compelled consumers into choosing glass at the same price as plastic.
To think that Coca-Cola would sell glass at the same price as plastic, temporary marketing stunts aside, is even more silly than thinking that consumers would legislate their ability to buy plastic bottles, where they have shown a clear preference towards, away from themselves.