Cost of this kinda plane ?

Here is a lite twin with 2-seats. It can be bought with different options from USD 86 000 - 100 000.

http://www.airox.cz/

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The engines for Max are from 4 000 - 17 500 €. Avionics minimum and gear selfmade etc. I figure a selfmade man does this at 10- 12 000 € from plans ( and less if you get a free motorcycle engine of 20-25 hp ) and kit with 50 hp certified engine and structure tested for 230 mph ( +6 -3 Gs )+ minimum VFR instrumentation the cost is near 50 - 60 000 €.

Is this plausible thinking ?