An E-tailing Group study revealed that unconditional free shipping is the #1 criteria for making a purchase (73% listed it as 'critical').

In another study 93% of respondents indicated that free shipping on orders would encourage them to purchase more products.

In yet another study, 47% stated that they would abandon the purchase if there was a shipping charge at checkout.

And just in case you need more proof as to why you should offer free shipping - consider the case of Amazon which author Chris Anderson shares in his book "Free". After Amazon implemented a free shipping offer, sales went up in each country except for one - France. Why? Because France charged 20 cents instead of free. Even though 20 cents is almost free, it didn't feel that way to people. When they changed the shipping to free, sales went up in France as well.

Therefore, you would get higher conversions even if you made the product more expensive to factor in the free shipping.

Because as David Bell, a marketing professor at Wharton, states:

"For whatever reason, a free shipping offer that saves a customer $6.99 is more appealing to many than a discount that cuts the purchase price by $10."