A study by TPI reveals outsourcing contracts deliver 15 net savings on average:
The sutdy has for the first time revealed the true cost savings delivered by outsourcing. The research, which examines outsourcing contracts awarded between 2003 and 2005, disproves widespread market claims that outsourcing can reduce costs by over 60 per cent. In reality, savings net of professional fees, severance pay and governance costs average 15 per cent and range between 10 per cent at the bottom end and 39 per cent at the top. 15 per cent is also the average level of savings anticipated when contracts are first let.
More details over here. So now you know the answer to how much outsourcing can save companies.