Gratitude is a humble trait admired in the best of people. There are an infinite number of ways to give thanks. People often say, "Thank you" verbally, in cards, in emails, texts, and social media posts. In my experience, there really is only one way to show gratitude: saying it sincerely and authentically. It's not just the only way, but it's also the best way.
Whether a person gets a "Thank you" in a note, hug, or written in the sky, the thought that goes into it makes the real difference. The recipient can tell if it's a sincere or not based on what it is, what it says, and how it's given to them. It doesn't matter if it's a 99 cent card or expensively sent by singing telegram, authenticity and sincerity matters.
Knowing that, whenever I send an e-mail, Facebook post, any other form of communication saying, "Thank you", I know that it HAS to come from the heart.