Hi Jenny,I use the Dermafix pen - so pretty expensive and had amazing results with it and made my money back pretty quickly so it was worth it in my opinion, I also use genosys professional only serums which definitely adds to the outcome (which people at home can't purchase from Amazon!). I can't really comment on cheap pens, but as for people using their own at home - they can go ahead. It's just like any beauty treatment, there will be people who do their own, like gels nails, hair dying etc. My clients come to me because they want a professional treatment and want my knowledge. Its easy to get wrong - I've seen videos on Youtube with someone using 3mm on their face with topical serum from Amazon - absolutely ridiculous
I'm all for people doing it at home if they get the correct information from their therapist and use appropriate tools for home care. I retail 0.25 and 0.5 rollers to my clients, but nothing higher than this. Anything higher needs to be with a professional in my opinion.