Spellsilver production down to 2/5 usual cost! They got here in one jump from 3/5 to beneath the 50% cost barrier. The level where different things start to become possible in the economy, rather than you just having a sales advantage over existing sellers, even if they don't get any more improvements from here - and they're still going strong.
Though it's still 2/3 if you only use tier-2 Prestidigitators. Or more like 90% if you use only non-core-Project Prestidigators (Asmodia reports).
(He'd be even happier if not for that lingering, recently reactivated part of him, wondering if his improved spellsilver processes actually matter to anyone, or if they're just something that somebody dreamed up to keep Keltham busy for unguessable reasons. Well, besides the obvious guess about 'Cheliax' or whoever only really needing him for his genetics.)