“He's tougher than a two-dollar steak!”

Veganism: The Fundamental Principle of the Abolitionist Movement, http://www.abolitionistapproach.com/veganism-the-fundamental-principle-of-the-abolitionist-movement/
Context: There is no meaningful distinction between eating flesh and eating dairy or other animal products. Animals exploited in the dairy industry live longer than those used for meat, but they are treated worse during their lives, and they end up in the same slaughterhouse after which we consume their flesh anyway. There is probably more suffering in a glass of milk or an ice cream cone than there is in a steak.

Source: Four to Score

A New Life (1961; repr. Harmondsworth: Penguin, 1968) p. 111

Source: On the Jellicoe Road

Often attributed to Twain online, but unsourced. Alternate source: "The whole principle [of censorship] is wrong. It's like demanding that grown men live on skim milk because the baby can't have steak." — Robert Heinlein, The Man Who Sold the Moon, 1951, p. 188.
Misattributed

Roughneck, The Life and Times of Big Bill Haywood, Peter Carlson, 1983, page 146.

Source: 2000s, Lines marking the introduction of Trump Steaks by The Sharper Image (2007)

Source: Iced

Source: An Introduction To Probability Theory And Its Applications (Third Edition), Chapter XIV, Random Walk And Ruin Problems, p. 349.