Sorry, c.i., with the interruptions in E mail notification I missed this one until noiw.
Like I alluded to before, there's really no basis to appraise newer artwork except for its perceived intrinsic value. An appraiser would probably not want to charge one for appraisals of new work that essentially are not of great value in themselves.
Number one rule in collecting art (or for decorating) should be, buy or accept the art because you love the work and want to enjoy it on your wall. Do not buy for investment -- the odds that the piece will increase in value to the point you can make money on it are not encouraging.
In pricing new paintings, one has to consider many factors -- the skill of the artist, their credentials (education, any previous exhibits and/or sales), the size of the work (only subjective as a wall filling abstract is often not priced more than a smaller representational work with a lot of obvious work in it), the demographics and other factors. What appraisers do is research the history of a piece including the consumate work of the particular artist before placing a value on it.
They normally won't word their appraisal as "market value" because, in the end, their appraisal involves some opinion (you would get two different appraisals from two different appraisers, although they likely wouldn't be off by much). If the artist's works has come up for auction and brought a certain price over several years, that's an indication of the market value. Not many artists qualify -- for instance, an experienced, qualified and experienced appraiser would not consider how much retail galleries in a mall gallery sell paintings for. They would likely appraise them for as little as 20% of what one paid for them. If one brought an accredited appraiser a Kinkaid painting, or even worse, one of the cheaply done reproductions, they may start rolling on the floor in gales of laughter.
The gallery I am a full time consultant for now, for instance, specializes in obtaining originals and prints from publishers, artists and galleries that has been slow in the marketplace due to several factors. They have an entire collection of a particular artist right now who's work sold for $1500.00 to $4000.00 at a well known multiple location gallery. They are priced at $600.00 to $1800.00 unframed. What does that tell you?