Orlyval is quite expensive (~7EUR for 7mins travel to Antony...).

There are additional possibilities :
- Orlybus (6.40 EUR) to Denfert-Rochereau ;
- RATP bus from Ory to Villejuif then Metro Line 7 (I think it's the cheapest one) ;
- Shuttle bus (2 EUR) to RER C Aéroport d'Orly - Pont de Rungis, then RER C to either Massy Palaiseau (then RER B to Paris) or Paris directly.