{It were well for him} (lusitelei aut(9369)). An old word, but
only here in the N.T., from lusitel(8873) and this from lu(935c), to
pay, and 	a tel(885c), the taxes. So it pays the taxes, it returns
expenses, it is profitable. Literally here, "It is profitable for
him" (dative case, aut(9369)). Matthew has sumpherei (it is
advantageous, bears together for). {If a millstone were hanged}
(ei lithos mulikos perikeitai). Literally, "if a millstone is
hanged." Present passive indicative from perikeimai (to lie or
be placed around). It is used as a perfect passive of
peritith(886d)i. So it is a first-class condition, determined as
fulfilled, not second-class as the English translations imply.
Mulikos is simply a stone (lithos), belonging to a mill. Here
only in the text of Westcott and Hort, not in  Mr 9:42  which is
like  Mt 18:6  mulos onikos where the upper millstone is turned
by an ass, which see. {Were thrown} (erriptai). Perfect passive
indicative from 
hipt(935c), old verb. Literally, is thrown or has
been thrown or cast or hurled. Mark has ebl(8874)ai and Matthew
katapontisth(8869), which see, all three verbs vivid and
expressive. Rather than ((885c)). The comparative is not here
expressed before (885c) as one would expect. It is implied in
lusitelei. See the same idiom in  Lu 15:7 .