How expensive is organza will depend on what material it is made from. Polyester organza can be more affordable and more accessible for decoration and casual items or clothing. Silk organza on the other hand is a lot more premium and expensive. Other factors like the fabric's quality, emboridery and use can also affect its price.
To increase the price of the couture collection, bridal wear and formal wear brands will use more premium organza for a more premium quality.