What you're fundamentally asking is 'why do our potential buyers think our price is too high?" and the most effective way to find out and regain control of the negotiation is to simply ask them.

As them why they think the price is too high. Most likely they are basing their opinion on comparative product value or alternative solutions or they are simply playing hard ball. The only other possibility is that they simply don't place as much value in your product as what you do which means you need to work harder at selling the long term benefits as well as the immediate gains.