We used AutoSlash.com and paid around $312 for 9 days for a Crown Vic. Thrifty even told us to return the car with an empty tank as their gas was $.20 cheaper than at the gas stations. So it was $392 but I'm not sure if this was the going rate. Didn't check the hawaii discount car rental website either. All the fees they add on makes the "deal" you get seem not as good! Try to get an accurate estimate on the actual total including the fees. To be quoted $175 for the rental, it sounds like it won't be so much.