Here's some sample prices from the trip. Prices were for two people.
Blue lagoon: $45.50 (3400 ISK)
Laugardalur thermal baths: $14.75 (1160 ISK)
Einar Ben restaurant (anniversary dinner) 4 course meal with wine tastings: $248.90 (18650 ISK) Pretty good deal as they kept refilling our wine glasses

Nordica Hotel + breakfast: $193.50 (11500 + 3000 ISK)
Saga Museum (at Perlan): $22.90 (1800 ISK)