Co-products, not considered waste at $55~60/barrel for the wholesale price and $120/barrel for the final sale price.
http://www.eia.gov/dnav/pet/pet_pri_wfr_a_EPLLPA_PWR_dpgal_m.htm
http://www.eia.gov/dnav/pet/pet_pri_wfr_a_EPLLPA_PRS_dpgal_m.htm
Some wells are being drilled for natural gas liquids like propane, butane and consider the Natural Gas as a side product.
Buy your own tank and you can shop around for the cheapest price, rather than being tied to one company and tank rental and bloated prices.