I believe the whole library music business model relies upon the payment of royalties, in order to be attractive for any composer worth their salt to get involved. If there's no back end payment involved for creators, then the up front payment is going to have to be unrealistically high to justify good composers getting involved, I think.
Would be interesting to hear what your clients be willing to pay, terminal 3, for an album of say 20 royalty free tracks (that they wouldn't be embarrassed to put on their work) complete with all cut downs / tune in & out variations, etc.
Royalty free libraries do exist, but veer to the 'pile 'em high, sell 'em cheap' tendency - which doesn't really encourage quality so much as quantity. But who knows - maybe your client will just fall in love with the material offered by
these guys. Their demo says it all, I think...
There's a thread over at
Sound On Sound Business Forum which piles into the subject (admittedly with daggers drawn), if you're interested.