Buy the Gallardo
If you want to buy a Lamborgini Gallardo but cannot find
it in the 'Buy Cars' section, then all you have to do is
unlock the Gallardo Cop Car by playing through Career
mode, select it from the 'Car Select' section, then here's the trick, press 'Back' (triangle), then view the 'Buy Cars' screen. The Gallardo should now be available to buy.
NOTE: When you press 'Back' from your Gallardo Cop Car, look
at the price of the car on the bottom left side of the screen. Now you know how much it costs already.