The original question is kind of like how much would you pay for a car? Do you mean a brand new Lexus with all the bells and whistles, or a twelve year old hyundai that never had any bells and whistles, or a highly competative Formula 1?
Hatchery silkie chicks run $5 to $10. Started silkies from breeders probably start at about $15, and can easily go up to $75 or $100 or more. Older birds whose potential is more apparent can be more.costly, and to some extent the breeder's name will affect the price.
Regular hatchery silkies, for a pair, I'd probably ask around $30-35. Depending on color, also. Colors besides black and white seem to sell better here.