I think the most immediate thing to do for troubleshooting is to dig into how the normal Soul Gems work. Figure out how filled Soul Gem price operates. The most obvious cause of the issue is that the filled price is an equation multiplying the base price, so having the price set to 0 breaks the formula resulting in having no value no matter the soul. I'm not in the right headspace at the moment to navigate the shenanigans of downloading the Bethesda launcher just to extract the Creation Kit into Steam, so I can't offer exact technical help. As for balance, I first need to ask what it is you want the conjured soul gems for. If it's just for recharging items, then I'd suggest looking into the code behind the Soul Siphon perk to instead have Soul Trap variants that directly recharge held items on kill so that it isn't offering a mass supply of grinding fuel. If you specifically want to support bulk Enchantments, I'd suggest looking for existing mods that add Enchantments which burn enormous amounts of charge or are super situational, alongside fishing for enchanted consumables that aren't rechargable in the first place. Find things that offer reasonable uses for that, instead of juggling a pile of different full-weight weapons.
