Is this really about the sims freeplay? I'm so confused... factories? I think you have the wrong game or something.
There are candle, pottery, jewelry and glass blowing stations that do cost a small chunk of simoleons but no factories, also you do not need to buy the stations again once you have them. You can either keep them on your lot or store them in your inventory for the next craft event. Though, if the station still has a number of crafts available before restocking and is a pottery, jewelry or glass blowing station, keep in mind storing them reverts that number to 0 and you will need to restock once they are placed again on a lot.
The game asks us to craft those supplies to win prizes in the events
If your talking about Laura Craft, she too is buy at your own risk because she does not automatically give supplies, you must set and collect from her each time she finishes or she will be wasted.
The crafting events require a player to essentially hover over your game through its duration or to timely check in every 2.5 hrs to keep up. And the bonus craft supplies has a limit per station per each time you set a station and you need to be present to collect those while your sims are working the stations. You do not get credited the bonus craft supplies from the stations upon the final collecting of a station before resetting. The crafting events are probably the worst in the game on demands from the players. Good luck.