I didn't hear any mention of NYC #3 as a speculative modern. I don't follow modern comics much, but that was a hot comic for time if I recall. Has that one run out of gas?
I assume with moderns, that comics have to have the ideal set of circumstances to not only increase in value, but to stay relevant ($ wise) on a long term basis. These would typically include low print runs, first appearances, and a place in one of the major universes (or in pop culture like WD). NM98 would buck the trend of the print run simply due to the breakthrough nature of Deadpool as a top tier character. But those don't come along too often. Would a low print run and a mid tier character provide any sustainability with price, or are all moderns doomed to large swings based on the flavor of the day?
What about something like Stars and S.T.R.I.P.E #0? Low print run (from what I can tell), first appearance of Stargirl who is still relevant in the New 52 (Justice League), and hinted to have a part in the Justice League movie. Certainly not a hot comic, but do those type of ingredients lend for speculation, long term appreciation, or are comics like these just to obscure to matter?