To add the same product twice in the invoice with different price, follow the below mentioned steps:
Step 1: Click on Invoice.
Step 2: Add customer.
Step 3: Add Product >> Click on Continue.
Step 4: Click on Add More Items >> Search and select the same product >> Click on Continue.
Step 5: Select the product to change price >> Click on Continue.
You can remove the existing price and add a different price for the same product.
Different price for the same product will be added.