Lambo's dont seem to be losing that much money, LP560's seem to have bottomed out for the moment at around 120k and LP640's are still fetching 150k for 06/07 cars, even late 09 examples are fetching around 180/190k and around this price for the roadster varient.
A great investment is a 6.2 Murcielago Roadster, 12-24 months ago, 120k would have got you one, a black Roadster sold around 2 weeks ago for 160k, these are going up in value as they are so rare.
Another great Lambo to buy now is the 07/08 Gallardo Superleggera, many think the Gallardo SE is the rarest Gallardo as only 250 were made, however because this was announced as a special edition, people thought they would be collectable and sort after yet the 07/08 Gallardo Superleggera was not announced as a special edition and with the LP560 due in late 2008, only 172 07/08 Gallardo Superleggera's were built and not many came to the UK. They are currently sitting at around 100k yet i bet in 2 years, they will have increased in vale to around 130k maybe more as people will become aware of how rare they are.