Iceland is not a cheap country to visit. The prices for car rental and hotels are far more expensive than in America and much costlier than in rest of Europe.
We rented a Hyundai Santa Fe for four days and it cost 66 063 ISK ie 755 EUR or 1030 USD (unlimited mileage, all insurances included). This was a good offer, we got much more expensive offers. RB Cars is a local car rental company, we were really happy with their service.
The cost for accommodation was 69 500ISK (800EUR or 1090USD), for five nights (breakfast included):
Fosshotel Nesbud - two nights, total 27 800ISK (320EUR or 430USD)
Hotel Framnes - two nights, total 26 200ISK (300EUR or 410USD)
Northern Lights Inn - one night 15 500ISK (177EUR or 242USD)
We spent for food 26 500ISK (300EUR or 415USD), mostly enjoyed the fresh seafood for that money. In hotel Framnes the seafood main course cost about 2500ISK (28EUR or 39EUR), the fish soup in Reykjavik harbor Fish shop was 800ISK (9EUR, 12,5USD).
Alcohol can be brought in Arrival Duty Free shop (sixpack of local Egils Gull 699ISK, 8EUR or 11USD ) or at Vin Bud liquor stores.
Our Hyundai Santa Fe used diesel. The price for one liter diesel was 120-129ISK (1,45EUR or 2USD), gasoline was with a little bit higher price.