Current panels are in the 3-400 watt each range. 60 cell grid tie panels are the cheapest but 72 cell off grid/battery charging not far behind, battery charging is less complicated with 72. Also the panel life is 25 years and there are used panels, usually smaller for sale too. Sometimes large systems get replaced for financial or tax reasons. Lead Acid Batteries are still the cheapest per watt and premium cells last 16-18 years.
Cost per panel has stayed close to the same but panels have gotten larger.