Because the pepino is very similar in shape, smell, taste, color, texture, and structure to a melon it is often called a pepino melon. But despite so many shared characteristics, the pepino is not closely related to melons at all, the resemblance being another example of evolution arriving at the same general point from disparate paths.
The pepino is a smooth, white, fist sized, eggplant shaped fruit with thin purple bands running down the skin which are disturbingly reminiscent of stretch marks. It is not often found outside of its native Peru and Chile because it doesn't tend to take transportation well. This is reflected in the $4.99/lb price tag I had to pay for this one and at .59lb, I was out $2.94... a fair price to pay for my innumerable readers (if you don't consider zero a number).
The skin is incredibly thin and the insides are colored with a more off white color. The smell is evocative of a honeydew melon, sweet but somewhat bland and, well, "mellony". The taste, while sweet, is even blander than the scent and, although pleasant overall, there is a slight hint of soapiness.
The rarity of this fruit cannot be attributed solely to its bad reaction to travel. If the typical bland supermarket fruit can beat this little melon mimic then I don't foresee it ever being in high demand.