We just reserved a car from Eldan for four days for about $200, which I thought was reasonable given that it includes additional insurance. Eldan comes very highly recommended. If you're seeing quotes of less than $300 for 10 days, including insurance, I couldn't argue with it. Seems cheap to me.
From Douglas Duckett's travel guide:
If you are renting a car, definitely do so on-line before you leave; you will save a lot of money over waiting to rent once you arrive in Israel. I strongly recommend an Israeli company called Eldan for rental cars. On my last several trips, they had the best rate, with a 20% discount for Internet bookings through www.eldan.co.il, and I have found the service excellent. Eldan also has a hotel in Jerusalem next to the YMCA; you can book the hotel with the car as a package deal. Hertz, Avis, and Budget also offer rental cars in Israel. Book through each company’s Israel web site (with the suffix .co.il), not the US sites or third-party sites, as you may not get the full price including the required insurance. I have used Avis in the past and was happy with it; see www.avis.co.il. Budget is a newer player in Israel, and I used them in 2006, getting a great rate at www.budget.co.il. I had a very bad customer-service experience with Budget’s Tel Aviv office, however, and others have also reported negative experiences. At all costs, avoid Sixt—their Israeli franchisee has scores of negative reports on TripAdvisor! I note that Thrifty and some other American operators now have a presence in Israel through local franchisees, but reports have been mixed. I would stick with Eldan. (And in Israel, Enterprise is Eldan, so just use the Eldan site.) Note: You probably don’t need an international driver’s license so long as your license has the information in Latin letters. If not, you may need to obtain the international driver’s license, which basically translates the information into English. But confirm what you need directly through your rental car company.