Totally agree but despites got 3 - 4 years experience in product I cant say I will be 100% expert and certification costs so much money as well.
You don't need to be a 100% expert. I myself am still learning new stuff about AA every now and then, despite my certification.
Also, the passing grade is 80%.
Have you taken the practice test? See here for instructions to access that: https://express.adobe.com/page/oNULBG45sdmaN/
If your company is a Solution Partner, then your company is entitled to discount vouchers for the exam too.