The Dennis the Menace comic strip by Hank Ketcham (1920-2001), on June 14, 1952, had Dennis tell his friend Joey a now-classic observation about Father’s Day:
 
“Father’s Day? Well, it’s just like Mother’s Day, only you buy a cheaper present.”
 
The book Every Day Is Father’s Day: The Best Things Ever Said About Dear Old Dad (1989) credits Brooklyn-born author Gerald F. Lieberman for the saying, but it’s likely that Lieberman (whose work began to be popular in the 1960s) had compiled an existing saying.
   
               
Wikipedia: Dennis the Menace (U.S. comics) 
Dennis the Menace is a daily syndicated newspaper comic strip originally created, written, and illustrated by Hank Ketcham. It debuted on March 12, 1951, in 16 newspapers and was originally distributed by Post-Hall Syndicate. It is now written and drawn by Ketcham’s former assistants, Marcus Hamilton (weekdays, since 1995), Ron Ferdinand (Sundays, since 1981), and son Scott Ketcham (since 2010), and distributed to at least 1,000 newspapers in 48 countries and in 19 languages by King Features Syndicate.
 
14 June 1952, Arkansas Gazette (Little Rock, AR), “Dennis the Menace” (comic strip) by Ketcham, pg. 3B, col. 4:
“FATHER’S DAY? WELL, IT’S JUST LIKE MOTHER’S DAY, ONLY YOU BUY A CHEAPER PRESENT.”
 
18 June 1953, Greenwood (MS) Commonwealth, sec. 2, pg. 4, col. 2:
Father’s Day is just like Mother’s Day only you buy cheaper presents.
 
28 May 1954, Record-Eagle (Traverse City, MI), “Broadcaster,” pg. 14, col. 1 ad:
Small Boy’s definition of Father’s Day: “It’s just like Mother’s Day, only you don’t spend as much on the presents.”
   
3 June 1954, The Daily Sun (San Bernardino, CA), pg. 24, col. 1 ad:
MODERN TEEN TALK—Father’s Day is just like Mother’s Day, only you don’t spend so much for the present.
(Fooshee Furniture Co.—ed.)
 
13 December 1956, Pomeroy (IA) Herald, “Pomeroy School Cyclone Siren,” pg. 4, col. 4:
Father’s Day: Just like Mother’s Day, only you don’t spend as much on the present.
   
5 June 1958, Hammond (IN) Times Earl Wilson syndicated entertainment column, pg. C-10, col. 3:
Wish I’d Said That: A youngster’s definition of Father’s Day: “It’s like Mother’s Day, Only you don’t spend as much.”
 
8 June 1958, Irving (TX) News Record, “Cupp’s Column” by I. B. Cupp, pg. 1, col. 1:
IT’S ALL A MATTER OF OPINION—Father’s day is like Mother’s day—only you buy a cheaper present. Thank goodness.
 
8 June 1959, Milwaukee (WI) Journal, Green Sheet, pg. 1 banner headline:
A Small Boy Says, “Father’s Day Is Like Mother’s Day, Only You Don’t Spend As Much’
 
8 May 1960, Atlanta (GA) Journal and Constitution, “Pioneer Mothers Were Saved From Many Jobs” by Leo Aikman, pg. 11-E, col. 7:
By the way, they say Father’s Day is just like Mother’s Day except you don’t spend as much on the present.
 
15 June 1962, Milwaukee (WI) Journal, “Every Dad Has His Day” by Paul Steiner (North American Newspaper Alliance), Green Sheet, pg. 1, col.
A small boy: “Father’s day is just like Mother’s day—only you buy a cheaper present.”
 
9 June 1968, Atlanta (GA) Journal and Constitution, “From a Wake-Up Vibrator To Snore Alarm, Dad Is King” by Leo Aikman, pg. 23-A, col. 1:
As the little boy explained it, Father’s Day is just like Mother’s Day except you don’t spend as much for the present.
   
Google Books
Every Day Is Father’s Day:
The Best Things Ever Said About Dear Old Dad
By Robert Byrne and Teressa Skelton
New York, NY: Atheneum
1989
Pg. 156:
Father’s Day is like Mother’s Day, except the gift is cheaper.
Gerald F. Lieberman
 
Twitter
Almost Live Radio
@jmessick
“Father’s Day is just like Mother’s Day, only cheaper!” a minor prophet
10:37 AM - 17 Jun 2007
     
Twitter
Michael Markman
@Mickeleh
Ancient Dennis the Menace cartoon; He’s telling Joey: “Father’s day is just like Mother’s day only you buy a cheaper present.”
12:41 AM - 15 Jun 2008
 
The Collection of Funny Tweets
Wednesday, August 1, 2012
More Funny Stupid Tweets
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10. Father’s Day is just like Mother’s Day, only cheaper!!
 
Twitter
Joker
@FunnyTunes
Father’s Day is just like Mother’s Day only you don’t spend so much.
9:22 AM - 15 Jun 2014
 
Twitter
104.1 The Hawk
@104thehawk
Father’s Day is just like Mother’s Day, except on Father’s Day you buy a cheaper gift.
2:10 PM - 17 Jun 2018