Why Offer Pre-Purchase Upsells?
There's a saying in ecommerce that goes, "She who makes the most offers will make the most sales," and that's the whole idea behind upsells: to make additional offers that will generate additional revenue that will grow your average order value.
Of course, upsells need to be done right, and a good upsell is a relevant upsell.
With post-purchase upsells, we make targeted offers based on what the customer just bought; with pre-purchase upsells, we base the upsell on what they're about to buy. Both are relevant to what we know about the customer, which is why our upsells have such a high conversion rate.
Simply put, by adding pre-purchase upsells to your funnel you will increase the number of offers you make which will increase your sales. Some customers will respond better to offers before they buy and others to offers after they buy, so you definitely want both.