What is the cheapest method to buy ETH?

As a keen observer of the cryptocurrency market, I'm curious to know: what is the most economical way for an individual to purchase Ethereum (ETH)? With the vast array of options available, from centralized exchanges to decentralized platforms, it's essential to identify the most cost-effective route. Could you elaborate on strategies that minimize transaction fees and ensure optimal value for one's investment? Understanding the nuances of each method could help new and seasoned investors alike make informed decisions.