Dear Hema,
I am not sure what you've mentioned is a mere statement of fact in general or what is actually happening in your concern. If it is a general statement, it may not be universally true for the simple reason that monetary consideration alone can not keep an unwilling employee under the services of an undesireable employer.Many more factors like job-satisfaction, promotional avenues,general work culture etc., are there.If it is an incident in your Company, it is indicative of the poor state of affair in so far as your employee compensation policy is concerned. Had it been an individual issue, you would have no qualms about justifying your proposed monetary concession to an individual employee for the sake of his retention.So, as a HR manager you are worried in this regard about the reaction of other employees means, it is true that your employees are under-paid.Therefore, real justification lies in dispassionate introspection and suitable remedial measures in this regard.