Hi again,
I just turned to a little book I have called "Victorian Cartes de Visite" by Robin and Carol Wichard (1999. Princes Risborough: Shire Publications) and found the info you wanted about costing. Just goes to show that books are still useful in this internet age

Daguerreotypes:
"The only country not to benefit from Daguerre's...gift to the world was Britain, where Daguerre took out a patent on the process. Few British photographers were willing to pay the licence fee and in consequence the process was restricted to relatively few professional portrait artists..."
Ambrotypes:
"In Europe, at least, the ambrotype process, requiring no licence and little skill, soon eclipsed the popularity of the daguerreotype and, in no time at all, framed ambrotypes were being offered for
as little as sixpence, which truly made photography available to all levels of society - even the poor....cheap, wooden-framed cases were ... manufactured, covered in embossed cardboard, papier-mache or, more rarely, leather."
Cheers
Prue