Also if you buy privately, you will need to find someone who knows how to pull it apart and crate it so that it does not get damaged in transit. I had to walk away from several really nice Sonexes last year because the sellers had no idea (even though they built the things) and no suitable contacts to do the packing, and I did not have the time to find someone. The USA is a huge place, so figure in finding your dream ship on one side of the country but flying it to the other side to prepare it for shipping. The nice aircraft always seem to be tucked away in obscure places off the main airline trunk routes. Looking at several prospects soon becomes expensive and time consuming.
IMHO, by the time you figure in all the costs, unless you are spending above $100,000 on your dream machine, the percentage of these add-ons against the total value does not make sound financial sense.