Wallpaper/Ringtone sites/Phonelines

Posted by BRAVO
Is there some rocket science theory behind setting these up?
Im keen to learn the logistics behind such services...I.e How does the wallpaper/tone get transfered to the requested phone..Where is it hosted etc

Is this an expensive venture to set up/maintain I.e Phones lines, hosting...webpages

Im sure some1 here can shed some light on this for me...
Thanks in advance