The silicon ones(last 5 to 25 years) run about $4-$5 a watt the amorphous (thin film) a little less (may last 5-0 years). If you use megawatt hour (000 kilowatt hr) a month you will need at least 3000 watts minimum. Therefore if your electric is .0 per kilowatt hr( $00 per month) the payback is around 25 years once you add the batteries plus inverters(batteries $50-$00 each)(synchronous inverter $3000 to$20000)(ie $5.00/.0=50 months at optimum output).Figure (depending where you live) probably only 50% so break even is usualy about 20 yrs.Ie you pay 20 years electric bill and hope nothing breaks(insurance not included) then you can start saveing money.
