You get a free ignis token of an unknown market value. To think you can by ignis for cheap after the snapshot is not a promise. So what you get is free Ignis for owning NXT. Yes NXT could actually become worth zero after the snapshot, but your ignis will likely be worth 2 times or more of the value of NXT going into the snapshot. So if you think the ignis token will be worth anything decent after the snapshot then NXT will be worth at least that much going into the snapshot.
There is no other way to get Ignis tokens without buying them for an unknown value after the snapshot.
Sat, Aug 26th between 06:45 - 07:15 UTC
Sun, Aug 27th between 18:45 - 19:15 UTC
Tue, Aug 29th between 06:45 - 07:15 UTC
Thu, Aug 31st between 18:45 - 19:15 UTC
Sep 09 - Sep 16 100,000,000 0.76
Sep 23 - Sep 30 100,000,000 1.05
Oct 07 - Oct 14 up to 100,000,000 1.45