The artist is engaged in self-expression and develops his individuality, and if there is a man who saw this personality and wants to sell his work, it is only good. And that means in this case "considered opinion"?

the artist creates a product that sells on the market.
Personal expression is not good for anything, just sit at home and express themselves.
The artist also has to produce images that can influence foreign audiences.

In my opinion, you harness the cart before the horse.

I believe that a person who is engaged in sales of works by the artist should not tell the artist: "You just do it - and do not do it. Write only the rings and only umber, and vkoem case nepishi squares - they nekupyat" It would no longer be an artist, and rather some form Tools in the hands of artdillera. Where is the individuality and self-expression of the artist. Another issue that the "correct" artist Nel are solved his individuality - is acceptable.

But what distinguishes gallery owner (or his hired director of the gallery) from ArtDilera?

"Do not buy from him," should be added. In addition, "which deals with sales of works by the artist has a clientele with their tastes and needs.
Look for another, which may sell all, even someone in a mortar.
Find a Takagi?

V printsipe ni chem.
Mozet byt 'odna raznitsa, kogda chelovek vladeet galereei, no ne zanimaetsia etim. Naprimer, vy mozete vladet 'zavodom ili aptekoi, no nichego tam ne delat', a tol'ko poluchat 'dohod s etogo biznesa. Tak rabotaiut i aktsii kompanii. Vy - sovladelets, no ne rabotnik.

In the "great principle".
But the methods are different.
Art dealer actually sells your item purchased.

Na komissionnyh toze rabotaiut. A voobsche, esli byt 'dotoshnym, to art dealer, eto chelovek, kotoryi prodaiot art. Usloviia sobstvennosti ne ogovoreny.

Antiques dealer, someone who sells Antiques
Drug dealer, someone who sells illegal drugs
Dealer, a person who sells on behalf of a company or organization

Art dealer - it is an intermediary between the seller and the subsequent buyer. Gallery other than sales of putting money into advertising, catalogs, magazines, albums, organizing exhibitions, etc. Gallery of the public, it's interviews, press conferences, media coverage.
Often gallery (if the owner can finance) offers for sale the work already owned by the gallery. And art dealers - work on the photos, they do not belong, if the buyer is interested, they begin to persuade the owner to sell the thing.