Recruiting is, for the most part, a commodity in endless supply. Or is seen to be anyway.
There's only one direction for the value of highly available commodities - down.
The current trend in recruiting is for employers to demand not warranties, but cash refunds.
Is say it's gone too far and its not commercially viable to accept cash refunds as part of the deal. Both employer and recruiter invest significant time and effort in finding the candidate in the first place, and both employer and recruiter carry out assessment to evaluate the candidates suitability.
If the employment deal does not work out for whatever reason, then the risk and responsibility lies with both employer and recruiter. Cash refunds mean the responsibility and risk lies entirely with the recruiter and that's not justified.
The most effective mechanism for dealing with a new employee leaving within the warranty period is that the recruiter gives a strictly-no-cash-refund account credit for the amount of the original invoice.
This means the employer is free to get the replacement from the recruiter, direct or some other source, and still imposes an obligation on the recruiter to find another person for the employer at some time.
If you are a recruiter and an employer requires a cash refund - just say no thanks to that relationship and move on to another employer who wants to do effective business in a commercially balanced way.
Just say no - and send all those great candidates that you find to a company willing to have a sound commercial relationship.