You most likely have your pricing set to Separate Product Pricing in your Inventory Settings and/or you are using Customer Groups.

  • Go to SettingsInventory Settings
  • Scroll down until you see Product Option Prices. Make sure you have it set to Added to base product price.

  • If you are using Customer Groups, make sure you have the group set to Exact Amount and No Discount.
    • Go to Customers → Customer Groups
    • Make sure you have Product Price set to Exact Amount and the Option set to No Discount.