The costs depends on various factors. i.e. the total size of the system, manufacture of the components but also regional price level and labour costs.
The prices are given in price per peak power (Kilowatt Peak, KWp), not price per square meter or square feet.
A smaller system for a residential home owner with maybe 5 KWp is more expensive than a large system.
If you prefer solar panels from Japan, US or Germany you also need to pay more than for products from China (which are not bad though).
Prices fro example in Germany for a key-turn system are typically around 1.350 EUR till 2.000 EUR per installed KWp (Date June 2012). Thus, for a 5 KWp system you can expect to pay around 7.0k– 10k EUR.