My pricing models don’t charge more for supporting additional programs unless it is a special case. Both Skies of Reality sets were initially for Reality only but I rolled in Carrara and DS support as an update free of charge. Skies of Terra came out including those three as well as Poser for the same price. HDR ProSets will be handled the same way when things are finalized there. I price my work on the underlying content like the maps included here.
Some info to show what you’re getting…
Skies of Terra - 6 presets at $12.95 = $2.15 per HDRI (Skies of Reality is the same and this is at non-sale price)
Skies of Economy - 30 presets at $29.95 = $.99 per HDRI (non-sale price)
If you are just using these for a single program you are getting them for less than $1 per HDRI preset at full price, $0.66 during the intro sale. Those who have the other programs will get more out of this set for sure, but it’s no different than how I’ve handled things in the past (other than having all apps supported at launch rather than updated).