Most companies offering $20 carpet cleaning have other motives. Such as:
Company A is not a carpet cleaning company at all. They are a national call center that simply takes the order. These days it is easy to get a local number in any city and they do this to try to appear like they are local. Company A will never tell you that they are a call center and will take your order and give it to a subcontractor. They will take the majority of the $20 a room and the subcontractor will be forced to try to raise the price once they are in your home to make money. Since the subcontractor is acting under the Company A name and since Company A does none of the work, there will be nobody to take responsibility when things go wrong.
Company B is a local company but they never intend to walk away with only $20 a room. They will charge you extra for everything from pre-treating to basic spot cleaning. They will also limit the sizes of the room so that just about every room will be considered oversized. Company B likes to say that they were voted #1 but they never produce any official survey or magazine where this is posted. This company also has a heavy duty cleaning method such as rotary scrubbing that works better than the basic method that the $20 gets you. They will force this method on you for a hefty additional charge.
Company C is new in town. They have just opened up their business with some outdated used equipment and think that the only way that they can compete with other companies is to offer a really cheap price. They mean well but will soon find that for $20 a room, they can not afford to maintain their equipment or but quality cleaning supplies. Company C will be forced to skimp on supplies, rush through jobs and use poorly maintained equipment. Quality will suffer and they will probably be forced to go out of business within a year.
None of these scenarios have good conclusions for the customer. It would be best for you to choose an honest company that charges a fair price for their services. I hope that you choose me for your Dallas carpet cleaning, but if not, I hope that you find an honest company and avoid the $20 a room trick.