Agatha Christie once said that she never thought she'd be wealthy enough to own a car - or too poor to afford servants. Nick Carraway, the narrator in Gatsby, had a Finnish maid to keep house and cook for him. Mrs. Hudson in the Sherlock Holmes series performs the tasks of both landlady and cook for Holmes and Watson.
Nowadays it would appear obscene that two men living as roommates would pay someone to cook their meals for them, or that a single man living on his own would pay for a maid. What are the factors (both economic and social) that led to the decline of servants as a middle-class necessity? What tasks would your average middle class family's maid perform, and which would be left to the family?
Edit: re-phrased question
There’s two books that I would point you to for this: More Work for Mother and Never Done: a history of American Housework, and if I remember right the authors worked together for a time before they wrote the books, so they’re basically two variations on the same core argument. I’ll outline their argument for the reduction in servant labor in the US, which is covered more in Never Done:
Industrial revolution sets off an increase in machines that replace some of the labor of servants, or make that labor easier. Better stoves and ovens, vacuuming services or personal sweeping machines, new cleaning products, all increase the ways you can “get by” at home with fewer servants or without servants at all.
Most people don’t like being servants very much. They don’t like living in their employer's house and under their rule, they want their evenings off, they like the freedom other jobs provide. When they can get a better job they will, and with the increase in industrialization, factory jobs provide a new source of employment for the ranks of women who otherwise would have had to be maids, and the supply of “domestics” decrease.
Fold into this employment shift the advent of “servant work” being done in an industrial setting and then brought into the home, see things like prepared packaged foods and laundry services. So this is sort of shifting that home work into factory work from domestic work. There were also early experimental “day care” things (which mostly failed, but then came back) and food services, imagine like a delivery service where you subscribe to dinner for a month, and then they deliver you a family dinner every day, but you don’t get to pick your dinner. (These failed.) We still have laundry services and day care around as examples of domestic work “exported” out of the home into a commercial/factory setting.
“The Servant Problem.” People don’t actually much like having servants around all the time, they complain that they’re lazy, they lie, they steal, they leave without notice, etc. People also really just like privacy and autonomy in their homes. They don’t much like having non-family members living with them or being forever in their personal spaces. The books both argue that when most people have the choice between convenience and/or saving money and autonomy and privacy, autonomy and privacy will win. This primary source is an interesting snapshot of one 1920s woman’s feelings on her “servant problem.”
So “too expensive” is a matter of both a reduction in the available domestic workforce and a redistribution of spending money towards other things, namely “servantlike” goods and services and investments in labor-saving “servant” machines. This Economist article actually has a really good overview with a comparison to modern-day Brazil.
Hope this helps! If we're lucky /u/agentdcf will comment in here too, he knows more about the shift in food labor from household to industrial.
Edit: oops, I did a lot of "why" but no "when." Maybe 1920s or so was the approximate point in America, as seen by that one primary source and also the uptick in "home economics" education for middle class women in high schools (the birth and death of Home Ec for college women has a slightly different trajectory) but the roots of the servantless shift go back much earlier.
Given their wage rates and persisting popularity, I'm not sure they have become "too expensive." Middle class Americans still resort to 2.5 million domestic workers that include maids, au-pairs and caretakers for elderly family members. Most of them now come from South America and especially the Philippines, the latter being the world's largest exporter of domestic help. See this recent Deutsche Welle article. The changing nature of the domestic worker labor market is beyond my scope of expertise. That said, perhaps we ought to reframe the question to ask how the role of domestic servants has changed among the middle class, not if it's become too expensive.
It's not that uncommon for a middle-class man to use a cleaning service, or something along those lines. Isn't that effectively a modern day maid?