Seeds are really inexpensive when you think about what you are getting out of the final product. One plant is around 2oz for me, thats 300-500$ worth of pot street value in MI. So I spend up to 100$ on seeds, 240$ on electricity to get it through its life cycle (lighting, pumps, fans- 2 weeks starting/stabilizing seeds, 1.5 month veg, 2 month bud), 20$ on the starter plugs, and 100$ on nutrients for 10 plants. Which is about $3k worth of weed for around 460$. Of course there is the occasional seed that doesn't start and the plants that get bullied out of the direct light by the bigger girls, but you are are still making much more weed than you would get on the street for that kind of investment. Unless you got really good connects.
When I get my taxes back early next I plan to create a breeding chamber. I heard of a spray that's really cheap that you spray on a limb of a fem plant and it makes that limb produce pollen, and then pollinates itself and other plants around it. The result is all fem seeds. I really like Power Skunk because it is potent and a good producer, I want to breed it with other good producers. I still have plenty of research to do on it, but I have about 4 months before the tax refund gets here.
Then it will be an even cheaper investment.