The Inferno patch notes state:
Datacore offers have been added to Factional Warfare Militia Corporations (250 LP and 250,000 ISK for a package of 5)
At a generous 2000:1 isk to Loyalty Point exchange rate, that leaves Datacores retailing at about 150k isk each.
When doubled due to < 40% faction control, prices for the losing side will be substantially similar to before the change
However, for those datacores offered by the winning side, the costs are halved (or quartered!), which is especially interesting for Mechanical Engineering datacores, which are offered by all factions.
Unless there’s a true stalemate, one of the four factions will be ‘winning’ and thus push prices down. It’s probably not a good idea to be holding too many datacores of that type…