What you get at each price
Under about OMR 25 you are buying a fitness band with a screen: step count, heart rate, sleep, notifications, a battery that lasts a week or two. These do the health-tracking basics well and the smart-watch parts poorly - no app store, no payments, limited replies.
Between roughly OMR 60 and OMR 120 sits the proper smartwatch: GPS built in so you can run without your phone, a bright always-on screen, proper sleep and workout tracking, and on some models an app ecosystem. Xiaomi Watch S5, Samsung Galaxy Watch8 and Apple Watch SE 3 live around here.
Above OMR 140 you are paying for materials, screen quality, and on the Ultra models rugged construction, much longer battery life, and dive or trail features most owners never use. Buy them because you want the battery and the durability, not the feature list.