I think it all depends on how people mix their kava. I think in Vanuatu fresh kava used to have 1000-1500mg per shell!
@Deleted User analysed the amount of kavalactones in a weaker shell of kava prepared Fijian style and I think it had 140-150mg of kavalactones (on average).
I guess it's possible that kava shells prepared a la Tongan have 70mg or less.
BTW, Welcome to the Forums!
I am personally a traditionalist and in my country it's not legal to sell ethanolic extracts of kava, but I always like hearing about new initiatives aimed at introducing new people to kava. I think as long as you use high quality root, your product could be a great way to introduce people to kava.