When you say layout I trust you mean the schematic to PCB conversion, which I refer to as 'design'. The reason why we offer the design phase for free (initially) is because we can only quote a R&D fee once this is done. It would be unfair and bad practice to charge clients even before we can quote them a final price - even when they decide not to proceed with our services.
However, if anyone requires R&D performed without the final prototyping of that design by us - we will be charging for this service - the amount determined by the complexity of the task as complexity means time.
You have to also understand that for each design we need to construct a part-list, and we use Farnell as the supplier - this again takes time.
Hope this answers all your questions!