Upselling, cross-selling, and downselling can positively affect your conversion rates in a number of ways.

According to research analyst Sucharita Mulpuru, the simple act of making recommendations for further purchases to customers can account for anywhere from 10-30% of overall ecommerce revenue. Over a decade ago, Amazon stated that upselling and cross-selling were responsible for 35% of the company’s revenue.

To be sure, this number is largely atypical. However, it’s generally accepted that upsells make up anywhere from 2-4% of a company’s overall sales numbers, and cross-sales represent up to around 2% of such (usually around .5-1%).

As downselling is more of an “on the fly” technique and is harder to track (i.e., salespeople aren’t likely to log instances in which they made a smaller sale in lieu of a customer turning away a larger sale), actual statistics regarding downsales are hard to pin down. However, it stands to reason that providing a more convenient or affordable option to prospects inherently nudges them closer toward making a purchase.

You can find more information in Fieldboom's blog: http://www.fieldboom.com/blog/customer-loyalty-upsells-downsells-cross-sells/.