What you buy or sell are by-products of the idea or knowledge. We don't really buy knowledge from educational institutes we buy their service and time they've put into setting up the place and finding the information. Just like a great idea, we would buy the end result of the idea. We can't buy the idea by itself because it's given to us without any negotiations.
Now when Conceptual Art comes into play, the actual artwork is the idea. If people are really going to pay for ideas that are basically given to them, then they're just stupid or aren't thinking straight. For example: The toilet roll that was sold for R3000, and "created- by Kendall Geers. It was an interesting idea, but the idea has already been "given- to me just by looking at it. Now that I have the idea, does that mean I have to pay for it?? I don't think you can really use the word "buy- or "sell- when it comes to Conceptual Art. Call it a donation or a sponsorship. This is where the biggest flaw in Conceptual Art lies.
The next big flaw is the fact that Conceptual Artists need props or objects so they can communicate the idea. Now wouldn't the props play a part in the actual Artwork? If we think about it in music terms, how are we suppose to listen to music if it's just in the musicians head? We need to hear the music thru the instruments he plays and thru his/her voice if he/she decides to sing. All of the instruments and his/her voice play an important part in the Art process and in the communication process with the listener. Now because Conceptual art is all about the idea, wouldn't those artists be contradicting themselves by making use of props and objects? If Conceptual art wants to be 100% what it claims to be, then it can only exist in the mind and nowhere else.
Several Conceptual Artists have claimed that Conceptual Art is the purist of all Arts. If I had to look at art in it's purist form, I'd probably have to inject myself with all sorts of drugs or just simply shoot myself.
