While the plot of this episode's undeniably funny, this (and an episode of the The Attractive Nuisance (1978), were actually inspired by a national scandal (instigated by a report on 60 Minutes (1968)) which said that due to the effects of the high inflation rates (especially on the retirement incomes of the elderly), many weren't able to afford decent food and some were resorting to eating pet food. Congress ended up mandating automatic yearly increases in Social Security (and other Federal programs) to help alleviate this problem.
The $200 per month Gertie was receiving from Social Security (in 1975) equates to $931.40 in 2018 dollars.