they have to be turned on a lathe, so basically it cost more to make them... yes and no; because of the price most acrylic calls are going to be hand tuned and acrylic does allow for a more crisp & loader sound... all of my acrylic goose calls are way easier to blow compared to the $30, even $50 calls that you can get of the shelfs... duck calls are different.. they don't require the air pressure that a goose call does so a $20 primos duckcall will get the job done in the right hands for sure; another great cheap call is the Hunter speacalties series.. double or single read models are very ducky!
good luck