I've listed some basic costs for France, Spain and Portugal. Hopefully this will give you an idea of the differences between the countries, especially if you are budgeting.

These costs are based on 2007 prices.

Item Paris Rural France Madrid Rural Spain Lisbon Rural Portugal
Campsite (2 people and camper van during summer) €25.00 €15.00 €20.00 €14.00 €20.00 €10.00
Glass of beer (from a café) €3.00 €2.00 €2.50 €2.00 €2.00 €0.90
Coffee (from a café) €2.00 €1.50 € 1.50 €1.00 €1.50 €0.80
Snack (takeaway) €4.00 €3.00 €3.00 €2.50 €3.00 €2.00
Typical lunch (per person) €9.00 €6.00 €7.00 €6.00 €6.00 €5.00
Fuel (1 litre of diesel) €1.30 €1.10 €0.93 €0.90 €1.04 €1.02
Pension hotel room (double) €40.00 €30.00 €33.00 €25.00 €25.00 €20.00
Hostel dorm bed €26.00 €15.00 €16.00 €14.00 €16.00 €13.00
Packet of cigarettes €6.00 €6.00 €2.90 €2.70 €2.50 €2.50
1.5 litre bottle of water (from a supermarket) €0.40 €0.30 €0.30 €0.20 €0.25 €0.16