cheapest way is to buy 3 24W cfls grow a bigg ass plant through winter and when spring comes you chop it and get about 100 clones...
cheapest 100 seeds you`ll find are about 300$ succes rate 90%,so 90 seeds
bulbs are 20$ a piece =>60$ electricity 10$/mo,soil 50$/50l other expenses 50$ and the seed itself 10$,cloning gear 50$=>around 250$.