10-15 fuel per grenade crafted, this is like the situation with G5 and G4 bandages, people want them, yet don't want to pay fuel.
The fuel cost is only questionably plausible with some degree of crafting boost, and the benefit isn't nearly as good as the cost required. People LOVE fuel, and they don't want to be throwing it away with these grenades when they could be using stock ones that work as opposed to these which make it easier, but costs fuel.
If I had the option of stock grenades and saving fuel, versus these for fuel, i'm literally throwing my fuel away (same for pre-update crafted active gear), and nobody wants to do that.
...Except if there was a massive, gamechanging increase in stat increase or if these craftable ones provided unique effects that would be very beneficial in a raid yet aren't lootable. Right now, the increases seem too minor of a buff to quantify the cost, and there are readily available lootables that do the work without the cost.
That's my two cents on the topic (they'll remain MY two cents, not throwing them away on grenades).