Although Jeanswest usually run a "two for $109" promo on selected styles, this "buy one get 2nd half price" offer will get you a similar discount on all styles across the section.
Also, you can get your order shipped for free this weekend by applying the relevant voucher code (see link below) at checkout.
While two pairs of the jeans with original prices of $79.99 are the ones on sale for $109 for two pairs, you'll be able to save $20+ per pair on all other styles in the jeans section with prices ranging from $89.99 to $129 a pair.
Here are some examples:
2x Mindy skinny 7/8th jeans for $134.99 (save $44.99)
2x Sadie Crop Boyfriend jeans for $149.99 (save $49.99)
2x Emily Boyfriend jeans for $165 (save $55)
2x Estella Prima skinny 7/8 jeans for $193.50 (save $64.50)
Also, you can mix and match various stiles instead of buying two of the same - you'll get the same discounts on equally priced items and if they're not 50% off the lower value item will apply at checkout.