Persian rug value means a lot of things to me but basically the most important factors that affect its value are authenticity, quality of materials, finesse of the knots and beauty of colors and design. i think these factors are enough to create amazing Persian rug value.
“Persian carpet value is timeless works of art that exude beauty, elegance and quality.”
In other words..
Valuable Persian carpets are to gaze into a world of artistic magnificence nurtured for more then 2,500 years. The Iranians were among the first carpet weaver of the ancient civilizations and, through centuries of creativity and ingenuity building upon the talents of the past, achieved a unique degree of excellence.
“Persian rugs are one of the most significant manifestations of the Persian art, life and culture which surviving through time, wars and empires.”
Ok lets discover it deeper…
Persian Rugs Beauty and Design
Achieving oriental rugs value through the use of design and color can only be described as an art form
Iran is the genesis of most motifs, patterns and traditional colorations produced in rugs throughout the world today.
Besides, Persian rugs value and its art value seems an unplanned effect but in fact this is an art form that is very dependent on symmetrical patterns, designsand the repetition of these patterns.
One unique aspect of the Persian rugs and carpets is their curvilinear designs. Curved-design weaving is much more difficult to execute than geometric one.
Today most oriental rugs, weather from Pakistan, India, or the Balkan, are based on Persian rug designs, and even China, with its own ancient and unique heritage, is now producing rugs with Persian schemes.
Color is a part of the essence of a Persian rug value, painting is also as important as design, clearly beauty of the rug depends on its color matches.
Imaginative, artistic coloring can mean that a poorly woven carpet or rug is nevertheless delightful. if the colors are wrong even the most technically perfect piece misses
In an oriental rug with beautiful coloring man be rich and dark or clear pastels or even…
Authenticity
Persian rugs have traditionally been considered the most expensive and easily able to resale of all oriental rugs, usually older and more collectible rugs from different parts of the worlds,
If you think that a fine valuable Persian carpet is too expensive,but why.. consider that it can take a family a year or more to create a single artistic carpet. It can cost 15000$ to 40000$. That seems like a fair price when compared to other art forms. And, it can be handed down for generations.
This assumption has generally held true. However, from the mid 1980s this situation has begun to change. 
Unfortunately, the traditionally high resale values of Persian workshop rugs can no longer be automatically guaranteed, though the finest examples are still likely to retain their value.
It is advisable, if you are looking for an investment, to buy the best. In contrast, the production of village and nomadic rugs has generally decreased, and the investment potential of better quality rugs is probably far more secure now than in the past.
Finesse of the Knots
As i explained in Persian Carpets ,
Valuable Persian hand-knotted rugs are made with single knot. This enables the rugs surface more distinctly and it seems flatter. In fact if a rug is hand-knotted not machine-made usually feels great in anyway.
In addition to these, knots per square inch is another important point, i covered this more detailed in Turkish rugs.. but i can give you a quick example here.
For example, curved lines in a rug’s design can be drawn more smoothly and gracefully in a Persian rug with many knots per square inch, just as a lot of pixels in a television screen allow for more natural looking lines. And also, rugs that are very finely knotted have such dense surfaces that light is reflected from them in an attractive way.
Quality of Materials
Other considerable factor that creates Persian rugs value is its materials quality, off course in some oriental rugs, weavers use synthetic fabrics that makes a lower value rather than natural fibers..
which are..
Natural: Animal or plant fibers which creates Persian rug value including Silk Persian rugs , Wool Persian Carpets , Cotton Persian Carpets , jute, animal hair, sisal
Synthetic: Man-made material such as viscose, rayon, nylon, acrylic or polypropylene/olefin
Why natural materials are so important for Persian rug value?
This is the right question, here are some points.. 
* Excellent Durability
* Don’t contribute to allergies or pollution
* Cleans better and stays clean longer
* With the combination of natural dyes, they give an artistic value
* Do not fade and do not deteriorate with age like machine-made rugs and carpets
* Generally absorbs and retains dyes well..
I could say much more about why natural materials is so essential in Persian rug value , i mean in all hand-made oriental carpets and rugs, however i covered the natural materials more deeply in Persian Carpets such as wool silk cotton and more..