If you're looking for a used saxophone, model 21/23 Yamahas and Selmer Bundys are plentiful.  The Bundys are dirt cheap and durable, although their keywork is considered somewhat dated.  Condition is everything.  There are probably more good Yamahas than Bundys floating around, since the Yamahas are more recent production and they are very well made.  If you're looking for a new horn, the Jupiter, Cannonball, Antigua, Kessler, and Saxgourmet Bon Fils brands offer good horns at better prices than Yamaha or Selmer.  Decent altos start between $500 - $1000.  Avoid sub-$500 horns from China sold under various brands by unscrupulous dealers.  If you have a question about a specific mystery brand, feel free to ask here again.