Is it wise to make concessions when negotiating with customers?

YES but when its not conflict with the firm policies.

some times making concessions will come back with benefits to your company

Absolutely - In their eyes ( the cusotmer) it could be seen as bargaining and in some areas this could be the difference between closing a deal and loosing it. If they feel like they are levering extra value , they usually are and it will be of great significance and value to the cusotmer in the specific negotiation. Value is very important to any transaction.

• To be seen to be making concessions in order to work with your cusotmer - improve the outcome of a service or delivery, or  to increase value of the transaction is of great significance in more ways than the obvious ways.

Yes it is wise as long as it will maintain the customer’s loyalty, and when it balances the interests of both your customer and your company, so It is up to your calculation.