A friend of mine has a Sigma 75-300 mm F/4.0 - 5.6 for a Nikon D40 and no D40. So he's got a spare lens he's willing to sell for 50 (which is about 35-40 USD). I just came back from holidays and found out (the hard way) that you can't go out shooting squirrels, rabbits and sparrows with a stock 18-55. So I'm quite interested in his 75-300. Is 50 a lot for this lens?