Lore wise they are disposable ships used to win battles of attrition, not decisive victories.
Makin them cheaper would indeed be interesting, but it's hard to portray this "battle of attrition" in a single battle. Lore wise they were used to wear down the enemies during months/years.
Im wondering if another possibillity could be interesting: Make them defend your colonies. Basically you can pay money to deploy drones to defend your stations, but unlike patrol fleets they do not regenerate once destroyed (they are pretty much disposable, lore wise) and you must keep paying to make more. This would really give a meaning to the "war of attrition", it's litereally your colonies who give you money, and you're using this money to construct drones that will make up extra defenses. It's literally your industry wearing down the enemies. If you get low on money, no more drones.
And, basing off on that, maybe we could also pay to have a drone fleet following our own, your drone fast picket could enter battle as a independent ally not controlled by you (matches the flavour of being drones, and also extra help, so they don't cost you DP), but again, they will cost extra supplies and money to keep, and if they are all destroyed, you have to visit one of your colonies again to bring more drones with you.