When was cheap at its height?

Just a quick note:

In response to a recent call for papers concerning quick, cheap printing in the United States, I did a Google Ngram search on the word cheap (and other synonyms). It was necessary to limit this to pre-1900 because the concept explodes in the early 20th century. Here’s the result.

It is curious that a bargain overtakes cheap in the 1790s and the 1820s. It looks like 1761 was not a good year for cheap things but that we were equally cheap in 1770 and 1890.

 Here is the cfp, if you haven’t already received it: https://printinghistory.org/call-proposals-2017/