Interesting question. Vans say the kit is complete except for fluids and paint, and that is basically true. However you still need to buy a tool kit and compressor, pay for freight, set up a workshop of some kind, pay extra for the optional kits if you decide to install them, pay for primer if you choose to prime, buy replacement parts when you make mistakes, pay for painting unless you like the look of bare aluminium and fibreglass, etc. Realistically, I think for a bare-bones ELSA RV-12 you should allow about 10% extra to build one, and another 10% for a basic professional paint job. Because the -12 is an integrated kit, it's hard to be frugal on the basic kit aircraft from Vans. However, it is certainly possible to save substantial money if you go EAB and buy an alternative engine such as a used Rotax, new Jabiru, Viking etc. and shop around for other items such as avionics and paint it yourself. I'm guessing you may be able to get one flying for around $55k. Others may be able to provide better numbers.