There is some scientific evidence that the temps generated by a pro-quality steam vapor machine (around 300 degrees Fahrenheit) are sufficient to kill, or neutralize, dust mite allergen. You can kill the actual dust mites at much lower temperatures, but to destroy the allegen - which is composed of dust mite fecal matter and the decomposing body parts of already dead dust mites - you need to get up around 300 degrees.
I offer such a service to my customers who believe they are allegic to dust mite allergen. It seems to take about as long to perform this process as it does to clean most carpets, so I charge the same rate as for cleaning W2W carpeting. Let me know if you want details as to how to do this. I do somewhere between a few and several jobs each year, so its just a small part of my overall business.
Other than this process, I don't use my steam vapor machine on carpets at all.