Hand knotted carpets started as a nomadic craft where carpets were made of sheep and goat wool. Over time, hand woven carpets became an item for trade when the admiration for its art grew. As the trade grew, so did the need to distinguish the tribes through the woven patterns. Thus began a process of people handing down their skills to their children, who built on those skills and in turn handed down the closely guarded family secrets to their offspring. To make a carpet in those days required tremendous perseverance. Even when carpet making developed to the stage of workshops, with several employees working on the same carpet, it was a question of months and often years of painstaking work. The leader would dictate through a series of chants to the other workers the color of the individual strands of wool to be knotted. When the time came for the tribe to move on, the loom had to be dismantled and the unfinished carpet folded as best as it could. The following season, it had to be put up again at some new oasis.

Factors that determine the carpet's degree of appreciation includes: fineness and intricacy of design, rarity and condition. Making hand knotted carpets is a long and tedious process. The precision of the pattern depends on how closely the carpet has been knotted and how short the pile is. The quality of the carpet is based on its density. The more the number of knots per square inch, the better the quality. Such carpets are also more durable. They have finer and more detailed patterns. A very good quality hand knotted carpet may have about 350 to 1000 knots per square inch (depending on the material). Designs on carpets vary. There are different types of designs such as pictorial, floral, geometric etc. The rarer the designs are, the higher its value.

A well-maintained Persian carpet that has no repairs or very few undetectable repairs, a smooth pile and no uneven fading, will have a distinct advantage over a piece that has been poorly maintained. Over the last 25 years, Persian rugs have increased steadily in value, confirming that they are a sound investment. This increase is due to an equivalent increase in the demand and an increase in rarity. An example of business forces that affected the price of rugs would be the embargo against Iran that was established in the 1980's and which ended in 2000. Persian carpets, new, collectable and antique experienced substantial increase in value during this period. This was particularly accelerated in the 1990's when the Iranian government passed a law limiting the number of carpets exported out of the country each year.

As long as there is a demand for Oriental carpets and output remains as it is, hand-knotted Persian carpets will generally appreciate in value over time.