noun
bargain-basement price; greatly discounted price
Used in commercial contexts to emphasize an exceptionally low price, often in advertisements or sales promotions.
この商品は大特価で提供しています。
This product is offered at a greatly discounted price.
大特価セールは今週末までです。
The bargain-basement sale lasts until this weekend.
激安 is a more casual, slangy term for 'dirt cheap', often used in informal advertising, whereas 大特価 is a standard commercial term.
Compound of 大 (だい, 'big, great') + 特価 (とっか, 'special price'). The reading とっか is a standard on'yomi combination.