I get what you are saying.. i have seen transplants look very whispy and thin etc.. but there are some results i saw on youtube that gave nice density hairlines and they really showed it up close and parted the hair in diff directions. Unless the video is a hoax, they def gave a high density hairline that looked great.. Maybe they have new methods now? if you only wanted a hairline done and use all your donor hair, why couldn't they make it a high density hairline?
here are some examples
http://www.youtube.com/watch?v=ImqKyDID2...ature=plcp

http://www.youtube.com/watch?v=-Aqolq7BC...ature=plcp