reiki practitioners have a choice to charge a fee or not charge a fee, some do, some don't, some trade services with others.  It is an individual choice. I agree with alchemist.
Also....the Reiki practitioners shouoldn't be doing a session if the intent is focused on anything other than the client, and that the intent is in the use and transfer of positive energy for the clients highest possible good. The Intent of Reiki practitioners isn't one which is focused on money, it is of one which benefits his or her clients to the highest possible good. But if the client doesn't pay for the session then they disvalue the service because no monies were exchanged. it's human nature.

Reiki, I believe works at it best when the client and practitioners intent align with eachother ( the intent of the practioner by giving a treatment is one for the clients highest good. the clients intent should be one of a positive nature or atleast open minded to the belief that healing is taking place, whether it's emotional, mental, or physical.  

I am new to this forum and I don't know how many of you are Reiki practitioners. I am a Reiki II practitioner. I use reiki on my car, to ensure I make it to work and back ome safely. I use reiki on food before I eat it. I send reiki when friends and family are going through tough times. The uses for reiki are endless, but the use should be one of the highest possible good.

For example friend went to a bbq one weekend with some of his friends. On the way there they drove by a house they had no idea was inhabited by gang members, as they drove by a couple of gang members started shooting at them. My friend having a concealed weapons permit fired back out of self defense wounding one of the gang members. my friend was arrested for attempted murder. My wife and I were devestated, and began to call some of our friends who are also reiki practitioners. to send reiki to him and his situation. I told my accused friend not to let negative thoughts into his mind about the court hearing, and to remain positive. The court hearing came three days later and all charges were dropped.
If the intention is for a persons highest possible good then the reiki being sent to a client will go were it is needed to in the client or a situation etc.  The benefits of reiki are endless. If the intention is of the highest good for all envolved.

Shokurei Koka