The cost of a link is determined by dividing the reference bandwidth by the interface bandwidth.
The default reference bandwidth is 108.
Bandwidth is a number between 110,000,000 and is measured in kilobits.
Cost is a number between 165,535. Cost has no unit of measurementit is just a number.
For OSPF to calculate routes properly, all interfaces connected to the same link must agree on the cost of that link. Therefore, if you change the reference bandwidth on one router, you must change it to match on all routers in that area.