Ocean Jasper is a rare form of jasper, which is a form of chalcedony. It is also known as 'orbicular jasper' due to the banded ring shape / concentric bands of colour, from "spheroidal igneous inclusions", which just means the weathering/erosion of the rock peels off in layers, like an onion.
This is quite a rare form of Jasper - hence the price. Found only in the Kabamby region of Northwest Madagascar - this stone was only collected by hand in remote tides and carried back the local village for processing. The prime location - the Mine of Marovato - was fully exhausted in 2006. Though smaller, less attractive deposits surface from time to time - the main bulk of what is available for purchase is just recirculating specimens mined 2 decades ago.
Since it is only found in one place in the world, and since all the best deposits have already been mined years ago, it is seen as quite rare - which is reflected in the price.
It formed as a rhyolitic flow, which is a lower temperature lava flow, and contains high amounts of silica.
The red comes from hematite, a form of oxidized iron. The brown comes from goethite. The yellow-grey can be from clay.
I like to sit and imagine these as little planets, with details such as green for forests, blue for oceans, swirls of colours for gas giants, etc. There is certainly enough detail to marvel and behold Earth's own "as above, so below".