An iCloud storage plan is an external disc space in a subscription model, it is not a measure of how much data you consume. Each month you will pay for access to the iCloud Storage external disc. If that space becomes too small then you have the option of moving up to the next plan in the range and pay the appropriate monthly rate: US $2.99 for 200GB; or US $9.99 for 2TB.
You are referencing the cost in US dollars. Apple lists here the various costs in all territories internationally. At the top of the page you will see a paragraph which details the size of the three available plans: 50GB, 200GB, or 2TB. The US $0.99 plan is the smallest of the three paid plans.