Is it possible to add an item to the cart at a different price than what the set price is on the backend?
IE If I have product X setup for $100. If customer comes to the site and a criteria is met, and product X is added to the cart, I want the price to be $60 rather than $100. However if criteria is not met, price is the original $100.
If you are on Plus, you can use Scripts to modify the product price https://help.shopify.com/en/manual/apps/apps-by-shopify/script-editor
This happens on backend. You control the logic.
Any other front end tricks are just exploits waiting to happend.