I agree that we probably are seeing the effects of significant accounting differences.
The “top” LACs seem to be spending about $20K-$40K/year on instruction per student.
Large student bodies (and big classes) create economies of scale that tend to reduce the cost per student.
Graduate and professional programs tend to increase it.
Amherst, Bowdoin, Carleton, and Wesleyan all show instructional costs per FTE student in the $25K-$30K/year range (according to IPEDS data)…
Vassar is slightly higher ($31K); Pomona and Williams are higher still ($36K and $40K respectively).
Davidson and Reed are lower ($21K and $23K respectively).
However, research universities are all over the map (Texas at $16K, Yale at $125K/year).
I don’t understand why a private university like Yale would be spending so much more per student on “instruction” than a top public university like Texas. More, yes … but not nearly 8X more.
The average full professor’s 9-month salary at Yale is about $193K.
At UT-Austin, it’s about $138K.
At Carleton College, it’s about $121K.
(http://faculty-salaries.startclass.com/)