the Tom & Will gig bags are good value, well made and reasonable well padded -
http://www.tomandwill.com/productdetail.asp?productid=33AS-465
- but no gig bag will protect your instrument against any accidental knocks or drops - I use a cheap gig bag for my alto and I spend all my time being ultra careful about knocking it against things and keeping it in a safe place, tucked behind the PA away from people loading guitar amps on stage etc and not getting drunk and careless - the phrase 'gig bag' is a misnomer, it's not something you'd want to take on gigs
If weight is a concern then the Jakob Winter Greenline suggested by Aldevis is only 1.25 kg and the J Winter Eastman Carbon Fibre is only 1.3 kg - the Greenline is probably a bit flimsy for heavy touring and aircraft cargo holds and the Carbon is a bit over your budget -
Saxophone Accessories
Alternatively the lightweight rigid foam filled cases like the Rosetti -or the Gator Lightweight EPS -
Saxophone Cases - Sax.co.uk will do a better job of protecting your instrument than a gig bag and both are cheap and lightweight.
For me the only excuse for using a gig bag is that I don't have a car, so dashing across town for the last bus home is easier with less weight on my back - I keep meaning to save up and get the J Winter Carbon fibre