DOLOMITE,CALCITE,ONYX or TRAVERTINE which marbel type is costlier?

Onyx is another name for agate. Both are defined as crystalline quartz. Not marble. There is so much onyx it is used to make trinkets for tourists.

Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. It is common enough that it is used as a building material.

Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, and cream-colored varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material.

I have no experience with any of these, except that I used to make agate jewelry in high school shop class. Prices might depend on what quality of stone you want and how far it has to be hauled to you.

Onyx

I've heard the white marble with the blue or blue/gold veins in it is a rare and exquisite find. Also, what can't be taken for 'granite' or 'gneiss' is of 'quartz' going to be more expensive.