It' all depends on quality, age & breed really - females I normally charge with indian runners at pol (Point of lay) £25, Sexed day olds I sell at £8 each & the same for aylesburys, & I always sell out of both breeds - Normally I have people wanting orders for more birds before their even hatched. Khaki cam bells we don't breed but we get off the large commercial farms at about 18months old in largish batches of females & sell those at around £12-£14 a bird, our call ducks we sell for £40-£65 a pair. (Females will normally hold their value but males on their own your lucky to get £5 for in any breed)
It all depends really on what you want ducks for, do u want layers, good broodies or meat birds & how many do u want? As call ducks & miniature apple yards are great pets & broodies - but need their wings clipped as can fly well & are noisy. Aylesburys are a good dual purpose bird - meaning they lay well but you get a good meat carcass, whereas Khaki campbells & indian runners are brilliant layers with both breeds laying over 300 eggs a year, but if you want them to hatch their own eggs only bantam type ducks tend to sit & hatch & rear their young - all my other ducks I've had aylesburys sit 4-5 times in 20 odd years & last year was the 1st time they ever sat through & reared some young. Bear in mind do you want ducklings & a male - if so great but be prepared to cull males out or eat them, & also remember all ducks need a lot of water - mine are in the water around 70% of the time & are messy buggers when not free ranging. My geese on the other hand although their waterfowl spend approx 70% of their time on land, even though all my bird have access to a few miles of river.