I made it from a 1 mm iron plate. After the suitable measurements and cutting, I used the power hammer, english wheel, a little shrinking at the edges, then the final touch was TIG welding. So I'm ready to call to life any fuel tanks or re-design an old one. The price is like 250 €, depending about the form and complexity.
I turned special feetholders for a chopper called: El-Camino. The main piece is decorated with 4&6mm drilled halls, and are separated by polished aluminum rings. The steel spareparts were powder-coated. A similar one's budget is between 150-260€.