Notice nearly all these dealer adverts mention trade in allowances and or financing terms.
Yes, overall US economy was booming during post war years, but not everyone was flush with cash.
Adjusted for inflation a washing machine selling for $329 in 1955 would equal $3,977.17 in today's money.
Average/median wage for men was $3,977.17. That works out to about a weekly wage of $76.50. These are gross numbers, actual net pay would have been less after taxes.
For all but the most affluent households new major appliances couldn't come out of housekeeping money. Thus, it came down to liberal use of credit in various forms to finance purchase of major appliances.
Popular myth of post war period was that women, especially married women didn't work outside of home. That wasn't true and government numbers back it up. In USA many homes were dual income at least for some time because it was only way to have what would be considered a middle class lifestyle. Be it saving to buy a home and or for things to put into it...
These dealer ad campaigns were all largely designed to get people into store. From there a skilled salesman could take things from there. Needless to say there wouldn't be many of whatever washer or appliance was offered as special deal. But "tell you what I'm going to do....".
There was much going on behind scenes.
By late 1950's advances in technology made many major appliances from 1940's seem out of date. More over thanks to other changes in economy and manufacturing (among other bits) it was possible by 1955 or so to purchase a more modern, better built washer or other appliance for less or same as what it would have cost in 1940's.
Huge second hand market allowed appliance dealers to make sales by offering older traded in merchandise for less than new. Maytag nearly to end of WW days had a liberal program with dealers in how latter could capture sales by taking in and refurbishing used washers.
One constant you see in major appliance adverts from period is how terribly sexist things were.
Advertisers realized they had to appeal to the housewife (as likely end user), but also to His Nibbs who likely (assumed) would he paying the bill.
Such "authority figure" advertising usually meant some man (who looked as if he never did laundry in his life) extoling virtues of this or that laundry appliance.
