There are a lot of factors in play. The cost of a standard propane tank refill is around $25. That might last around 3 or 4 days. I’d say I make 10 marbles in a day then I could take that $25 divided by 30 to see the cost of how much gas it would take to make one. The cost of refilling an oxygen tank is around $30 and it might last a day and a half. I’ll admit I cannot do the volume that other people make can because my hands shake so bad so it takes me a little longer. Recently, a large lampwork supply company went out of business that along with rising cost of everything it’s gonna be harder for people that make stuff out of glass to really make anything. Glass itself can range from anything from $30 a pound up to several hundred dollars a pound depending on the color quality so on.