No problem with your woodworking, if it makes you happy doing it. You don't have to compare to the artwork boards that were posted above, or meet some minimum level of satisfaction of this board.
What you have to recognize is what your market is, what your skill level is, what your interest level is, and how much is reasonable to charge for the level of quality you can or choose to produce.
I personally wouldn't put in the time it takes to make boards of the quality level you are making to sell them for $70. I would choose to create things much better designed and executed, and charge more for them. That is what rewards me, and what pays me enough to make it worth my time. However, it obviously is worthwhile to you to do so, and you are somewhat proud of them, so it's great for you. As long as you can find buyers, continue to do it and try to improve and explore work that causes you to increase your design and execution skills.
To answer your original question, Yes, you can probably teach your friend to make stuff of the level that you make it, if you have the teaching skills, desire, and patience it takes. Your unasked question is "should I try to teach him". Only you can answer that; if you get satisfaction from passing on the knowledge you have to someone else, go for it. If your ego can stand having a student get better at the craft than you are, would be a help. That is always my wish for the people I try to assist with learning, I would very much like them to quickly surpass me in skill and talent, and go on to do great things.