Kemo Sabi, which way did they go?
Remember that no single comparison is the whole story. Condition, completeness and provenance must be considered as well. Now you should begin to go through the Leach listings, identify those of interest, select "Click for Detailed Record" and enter some of the details in the Abe [or other] search field. The search results tend to show that there are multiple copies on the web. Of course no book dealer of the pre-internet age anticipated their pricing could or would be carefully analyzed twenty years later. That Mr. Leach's valuations have stood up so well is a testament to his skill. It's a little like handicapping, at a high school graduation, who will be rich by the time they are 40. The "then" and the "now" are in plain sight and very easily compared. Sometimes you know and sometimes you guess.
Every person will obtain somewhat different results because we will search different items in different databases and use different terms in the searches. Mr. Leach's titles are not always reliable while the printer, place and date printed are. In the era before computers there were mimeograph masters that required Jesus' typing skills, Mary's judgment about what would fit on a line and Josephine's help in correcting errors. This simply means we need to be flexible in how we search these records. They are truly PC as in pre-computer.
Here are some random examples of comparisons between these Leach and ABE listings.
Gleason's Pictorial Drawing Room. He offered Vols. 2-5 for $200.00. Single complete volumes now command $300+.
No. 140. Thayendanegea, The Terrible; or, The War-Eagle of The Mohawks. A Romance of Early New York by Ned Buntline. His price was $20. If you wanted it you should have bought it. ABE has fifty million books for sale today but no copies of this one. Mr. Buntline's other volumes seem to be worth about $60. A manuscript of one of his many works is available on ABE for $800.
CHART OF DOMESTIC COOKERY, AND KITCHEN RECEIPT CALENDAR. Particularly Adapted To The Wants Of The Common People. Domestic Economy.  This one was $75.00. I didn't find any copies of this one but I did an additional search for Skinner & Blanchard, the printer and the year 1844. One of their other books was listed and I mention it here in case this is in your specialty:
Every Man His Own Cattle Doctor; containing the causes, symptoms, and treatment of all the diseases incident to oxen, sheep, and swine; and a sketch of the anatomy and physiology of neat cattle. This rarity is $165 but of course it is not the same book.