Texting demonstrates wireless companies love to charge based on protocol independent of costs. Also, throttling bandwidth does not necessarily hurt latency. So, simply charging more based on congestion is more useful than high vs low latency packets. If customer X is willing to pay 5$ to watch a cat video online wireless companies would live to be able to bill this.

As to upgrading networks, the wireless industry is pulls in $187.8B per year and spends $32.1B on capital investments. Yes, the network is expensive, but it's less important to there bottom line than you might think.