A discount percentage says little about the real market price. Compare the final price, recent price history and the terms of the offer.
Compare the market, not the crossed-out price
The “old price” can be higher than the normal price elsewhere. Checking a few retailers tells you more than a large discount badge.
Check the exact version
A cheaper listing may differ in size, accessories, warranty or model year. Compare the exact SKU and specifications.
A discount does not make an unnecessary item useful
Savings only exist relative to a purchase you already intended to make. If you do not need the item, a 50% discount is still money spent.
Look at total cost
Shipping, taxes, installation and consumables can erase the apparent bargain. Compare the complete cost, not just the listing price.
Bottom line
Keep the solution simple: start with the most likely cause, change one factor at a time, and observe the result. That makes it much easier to identify what actually works in your situation.