Left handed instruments are not common. Sometimes it is possible to convert an instrument to being left handed easily. Sometimes it is difficult. To build a left handed instrument is no problem at all, there are only a few alterations to make.
What alerations are necessary
If the soundboard of the instrument is not symetrical, then it is necessary to reverse the location of the struts or braces. My instruments are symetrical internally so this is not something I have to worry about. This also means that any techniques I use to produce a good top are not lost in the process. The next alteration is the fingerboard. Usually the fingerboard is not completely level. There is usually a dip in the bass side to accomodate the greater range of motion of the bass strings. The nut will also need to be different. The width of the slots varies from string to string. The saddle, if it does not have any separate compensation for each string will not generally need altering.
A left handed guitar is no different to me than a right handed and as such I do not charge any more to produce these instruments.
