And IMO, using magic in an industrial way always comes at a price. Those undead make great reapers during harvest, until a necromancer cult got involved and used them to destroy the town, or the locals became infected with some undead rot or something. That decanter was very useful for years, but one day water elementals began coming out of it and destroyed all the reclaimed woodland. Residual magic from constant use of those streetlamps opened a gate to the positive material plane etc. This may seem unsporting, but you're doing this to NPCs, so you don't have to play fair when they try to apply magic to industry. If the PCs try it, well, they can try and change the world if they like, that's part of what they're there for.