The whole chicken / beef thing has been misunderstood by the author - chicken was never the expensive alternative to beef. The author seems to have been masively misled by the (false) quote of Hoover "a chicken in every pot and two cars in every garage". Hoover never said this. My best reading of the history seems to be:
16th century: (Henry IV) "If God keeps me, I will make sure that no peasant in my realm will lack the means to have a chicken in the pot on Sunday!"
1928: (Hoover) "The slogan of progress is changing from the full dinner pail to the full garage."
1928: (Republican campaign flyer) Title "A Chicken for Every Pot", text includes "Republican properity has... put the proverbial 'chicken in every pot'. And a car in every backyard, to boot."
It's clear that in 1928 chicken wasn't an the indicator of wealth that the author things; it was (as the flyer says) proverbial.
According to the charts in The Rise and Fall of American Growth we've gone from eating 3 times as much beef as chicken in 1800 to eating 60% more chicken than beef. This[1] shows that since 1960 beef has gone up in price by a factor of 2 relative to chicken. So all the evidence I could find supports the author's conclusion even if I don't have any data on relative meat prices going back to 1900 or so. If you've got some data that actually contradicts the authors claim about food prices I'd love to see it but given the congruency I found I'm willing to accept their claim.
For reference, the 'smell test' that lead to me thinking twice about this is the energy cost. Small animals don't have to live as long to reach full size, so you don't need to spend as much energy (food) keeping the existing mass of the animal alive while it's growing new mass. That's why (very roughly) the cost of common farmed meat is normally chicken -> pork -> beef.
It seems the main reason chicken was expensive was that it was seasonal and labor-intensive. Someone on reddit writes:
> Chicken, and eggs, were until the mid-20th century, a seasonal food. Chicken more than a year old is very tough, requiring hours of roasting or boiling to get a fairly tasteless end result. Most chickens lay their eggs in the spring and summer, petering out over the year. Old recipe books will have different instructions for "December" versus "April" eggs, given the quality of the yolks, which didn't used to be the uniformly pale color that industrial eggs look like now. So when the eggs would hatch, the young males would be culled and eaten right away by households, but the variety of cuts were few and the market to sell chickens incidental.
Let's fast forward to the twentieth century. Unlike cows and pigs, who are irregular but large, chickens resisted the assembly line innovations of industrial production because they were irregular and small, which means they needed lots and lots of labor to process them.
The fact that the proverb was still in use seems to indicate that chicken was still percieved as a luxury good at this time? Today nobody says "a chicken in every pot", presumably because chicken is cheap.
I googled a bit and found "Management of Young Chicks" by P.H. Jacobs, from 1888, which says[1] "A half-pound chick sells at $1.50 per pound ... A three-quarter chcik sells at $1 per pound. ... A 1.5 pound chick sells at 50 cents per pound ... A pound chick sells at 75 cents."
Meanwhile the price of round steak in 1890 was apparently 12.3 cents/pound.[2] So at least at this point, chicken seems to have been more expensive than beef.
By the 1930s the prices of beef and chicken seems to have been about equal [3,4]. This makes sense, because apparently the 1920s was the breakthrough time in the chicken industry, seeing both the discovery of Vitamin D (allowing keeping chickens in confinement all year, and letting chickens thrive during winter), and also the first broilers (chickens bread specifically for meat rather than egg production). [5]
So the time when the Hoover campaign made the slogan about "a chicken in every pot" also seems to be just about the time when chicken prices had started to come down and making that feasible. But people were still eating much less chicken than pork or beef [6]; presumably people had still not changed their perception of chicken into an everyday food.
16th century: (Henry IV) "If God keeps me, I will make sure that no peasant in my realm will lack the means to have a chicken in the pot on Sunday!"
1928: (Hoover) "The slogan of progress is changing from the full dinner pail to the full garage."
1928: (Republican campaign flyer) Title "A Chicken for Every Pot", text includes "Republican properity has... put the proverbial 'chicken in every pot'. And a car in every backyard, to boot."
It's clear that in 1928 chicken wasn't an the indicator of wealth that the author things; it was (as the flyer says) proverbial.