How to know if a price is actually a deal
Compare the same item, not the crossed-out price. A price is a deal when the same item costs less somewhere else right now. A crossed-out number on the page is not proof. Sidelane looks for that item at other stores, puts exact matches first, and then shows the lowest price you would pay.
What the card can and cannot say
Shipping is unknown unless that store shows it. Tax is only an estimate after you add a ZIP. Sidelane does not claim a total that includes shipping, tax, and fees.
A discount code appears only when one is printed on the page. Sidelane does not invent coupons.
If the page you are on is already the cheapest match, the card says so.
A note about scams
Sidelane flags a listing only when the page itself gives a reason. A low price alone is not treated as a scam.