How much does it cost to buy WIFI?

Excuse me, could you clarify what you mean by "buying WIFI"? WIFI is generally a wireless network connectivity technology, not a tangible product that can be purchased in the same way as a smartphone or a computer. If you're referring to the cost of internet access that utilizes WIFI technology, that can vary widely depending on your location, the provider, and the speed and quality of the service. Could you please elaborate on your question so I can provide a more accurate answer?