Yes, it is even possible to get all 7 possbile girls into the harem (not all at the same time obviously) without using either the necklace or the pendulum. You just have to be carefull about harvesting plus points and avoiding minus points. In general the effort and planning required to get the plus points outweighs the weekly maintenance fee of $5 for a girl. Getting a girl back into the harem takes at least 1 period, maybe 2, to get the point and ask her. That one period may as well be spent in the food unit or the lab to earn the $5 to pay for the girl. I have never found the $30 needed to pay for 6 girls a drag on the treasury. The money was always there without any real effort.