There appears to be several claims to break down here, but the main two--that Sam Altman says OpenAI is spending "tens of millions of dollars" processing chatbot queries with writing etiquette, and that saying "please" and "thank you" to OpenAI actually does cost money--are true.
Firstly, the response to the original question on X comes directly from Sam Altman's certified X Account. He writes, "tens of millions of dollars well spent--you never know." This stands as a primary source and proof that this is a real quote by Altman.
Sam Altman on X: "@tomieinlove tens of millions of dollars well spent--you never know" / X
Next, the below New York Times article works to explain the details of how writing "please" and "thank you" to AI costs money. The article quotes a professor of physics at George Washington University, Neil Johnson, who says that using ChatGPT "involves electrons moving through transitions--that needs energy." Johnson adds that said energy costs money, which he expands upon by likening the processing steps of an AI bot to opening a package; every extra word is more packing material through which the bot sifts before arriving at the actual product/content. In other words, adding "please" and "thank you" in writing to chatbots only adds extra words (which require extra costly processing power) for AI to compute.
Saying ‘Thank You’ to ChatGPT Is Costly. But Maybe It’s Worth the Price. - The New York Times
Additionally, this Washington Post article adds more context to the quote by revealing how AI processing requires massive amounts of water to cool the heat it generates from processing. Providing this water to these machines, of course, costs money as well, and Altman's claim that using only a couple extra words per chatbot interaction costs "tens of millions of dollars" suddenly no longer seems outlandish.
How much energy can AI use? Breaking down the toll of each ChatGPT query - The Washington Post
Between the primary source of Altman's certified X account and these two stories from credible news organizations, one can conclude that Sam Altman actually made this claim, and also that the claim is true.
However, that he said this money is "wasted" (as it says in the original thumbnail for this News Detective post but not in the below description) is false. In fact, Altman's quote implies that the expenditure for these niceties is "well spent," and the body of the above New York Times article addresses the implications of being polite to chatbots despite the cost. The Futurism article linked by izzy_savannah (Sam Altman Admits That Saying "Please" and "Thank You" to ChatGPT Is Wasting Millions of Dollars in Computing Power) claims that Altman thinks using this etiquette wastes money, when he in fact, based on his original X post, he does not. According to their "About Us" page (About Us - Futurism), Futurism is independent and appears to have no political affiliations/motives to bend the truth of this story, so I would chalk up the misleading headline to an innocently poor choice of words. As of now, whether or not using "please" and "thank you" is a waste of money remains to be seen and stands as an opinion.
To break it down:
Sam Altman said this quote = TRUE
Using "please" and "thank you" with AI costs money = TRUE
Altman thinks this is a waste of money = FALSE
Using "please" and "thank you" with AI is a waste of money = OPINION
