A couple of things that may help. First of all, you can often get much better rates through AAA. I checked AAA rates (go through the AAA website for the best rates) for Logan Airport, arriving on the 17th and dropoff on the 20th, seeing an Intermediate car for $57/day ($223 total). Costco is also often an excellent choice for good rental rates. Secondly, it's really much too early to snag a good deal on a rental car. You can reserve something now, but to get the best rate you should check back every few days to catch when the rates drop (they often do). Then you book a new reservation at a lower cost and cancel the old one. I do this "rate hopping" all the time and have had cars for as cheap as $100 week, total cost. The magic window can vary, but on average I've snagged the best rates anywhere from 5 to 10 days out from the pickup date.