This post could also be subtitled, "there's no such thing as a free lunch". I see on almost a daily basis people who think they are getting some sort of deal and saving money by finding a "experienced", or "knowledgeable", friend to teach them how to climb rock or ice, ski, learn about mountain safety, etc.
It does not work: 99.9% of the time, and you get exactly what you pay for. Plus, when you are talking about certain activities such as mountaineering, ski touring, ice climbing, etc., it can be life-threateningly dangerous.
Let's look at the person put in the role of "instructor". In my experience usually this person is someone who has practiced the activity in question for a brief period of time (1 to 3 years) and due to the human dynamic, the "instructor" assumes a role far beyond their experience.
It takes about 10,000 hours of practice to become proficient at complicated activities such as climbing rock or ice. Break that down you come up an average of 1000 hours per year of training time over a ten year period. That's 20 hours per week of doing the activity in question. That 20 hours does not include the time you are using to drink an espresso at the climbing gym bar or sitting in your car on the way to the crag.
There is no substitute for training volume - everyone has to pay their dues. The people who think they are talented, or genetically gifted, or whatever, and delude themselves into thinking that the above does not apply are only fooling themselves. On top of this, someone who is put in the role of transmitting information and guiding the learning process needs a very wide palette of teaching experience similar to, if not more than, the volume needed to acquire the skill itself.
Yeah, it really pisses me off to come along and see someone assume the role of knowledgeable instructor, guide, trainer, climber, alpinist, etc., before they have put in their time. It is simply insulting. I mean when I hear a person talk in a way that implies mastery when they've climbed a few bolted routes, at best can red point one 5b that fits their style in the local climbing gym, have climbed two single pitch WI3's (hanging on every other ice screw), or "done" a classic alpine route with a paid guide, well it makes me want to puke.
If that is the type of person you want to learn from, well that's what you'll get and you'll save some cash. Quality? What quality.
The argument from the "student" is that they are a person looking to save some money and it usually goes along the lines of, "I can't afford it", or "It's too expensive", or "I'm only a beginner, I don't need somebody so good", etc. This is also a fallacy.
I can see in the first 30 seconds whether or not a so-called beginning climber, skier, mountaineer, etc., has worked with a proper professional or not. The learning curve in the beginning of acquiring a skill is extremely steep. If you chose to screw around and waste this opportunity, you will pay for it over and over again. How? Well you will eventually have to go back and fix every little imperfection, bad habit, sloppy technique, etc., step-by-step. It is much, much harder to override old habits in the nero-muscular system as freshly embed new ones.
In the end, a person may save some cash in the short term but will eventually come to regret not investing in themselves at this very precious time of learning something new.