Add value, not cost
It's natural for prospects to try to negotiate the best terms possible for their company's investment.
Source: Sales trainer Tom Reilly
One way effective salespeople negotiate win-win outcomes is by offering prospects more value in return for something else, whether it's a bigger purchase or a longer service contract. This way, instead of adding costs, the salesperson is providing additional value (and getting something in return).
The important part is that the prospect views the salesperson as someone who's interested in serving his or her needs. That goes a long way toward building trust and buyer loyalty.