Taxes: Local state taxes around $3400.
The cheapest route would probably be following the factory plans closely and not trying different things like I did. However, now that I have tried some of the changes, the next builder does not have to have the same extra "trial" expenses. Some of my extra cost was emphasis on performance features like electronic ignition, SS exhaust, IFR, etc. I probably skimped somewhat on interior finish - leather seats or whatever. Initially I never expected the cost to go over $75K and would have hesitated if I thought it would be $90K. But as I went along, I added different features until I had the combination I wanted. And in retrospect, I did not pay for the whole thing at once - but over two+ years with an initial $65K that I saved up. For an average builder taking 5 to 10 years the yearly cost would probably not be bad. And where can you get a certified 200kts cruise machine for under $100K?
Then I still need about $1000 for fuel/oil cost for 40 hour test period, then IFR lessons.... shucks.... I am helping the economy. The government should send me a thank you note.
Some insurance companies are hesitant to insure aircraft with few flying. But I know for a fact there are at least two SQ2000 flying, registered as something else for various reasons.