Should there be an “apostrophe-s” following “of somebody”?
There’s a problem that always puzzles me.
Examples of the problem goes like:
“……, you should have made more of the fact that Sandy’s payout to this cause is more than double that of Amy’s, ……”
In this case we put an apostrophe-s after “of Amy”

whilst another sentence goes:
“……, in terms of dietary expenditure, John had the greatest cost of it at $1000 per day, a figure which dwarfed the one of Jamie, ……”
Now we have no apostrophe-s after “of Jamie”

Can anyone explain the reason for such a discrepancy please ?

Question

Should there be an “apostrophe-s” following “of somebody”?
There’s a problem that always puzzles me.
Examples of the problem goes like:
“……, you should have made more of the fact that Sandy’s payout to this cause is more than double that of Amy’s, ……” 
In this case we put an apostrophe-s after “of Amy”

whilst another sentence goes:
“……, in terms of dietary expenditure, John had the greatest cost of it at $1000 per day, a figure which dwarfed the one of Jamie, ……”
Now we have no apostrophe-s after “of Jamie”

Can anyone explain the reason for such a discrepancy please ?

Answer

In the first example, the "possession" (grammatically speaking) is omitted.  (i.e. you could say "...more than double that of Amy's PAYOUT).  Although omitted, the structure is the same.

The second example does not use the same format.  It uses the "of" form of possession - "one" is the subject of possession, followed by "of" and the possessor "Jamie".  In this case, no apostrophe-s is used.

I think the confusion is from how "that" looks like a possession - it isn't.  I can't say "I like Edward's that."  But I can say "I like Edward's one." (of course, you must previously state what "one" this is - through context or through explanation.

Hope that helps!

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