How can I get the costs of a newly created business (E-2 visa, proportionality test)?

I strongly recommend that you retain an experienced immigration attorney. The E2 process requires a business plan which should assist in determining the required investment and operation of the business. It is a complex process and doing it on your own may lead to more headaches later on. Once again, retain an experienced immigration attorney. Best of luck!

$100,000 is the bare minimum ... and I do mean bare minimum size of an investment that 'might' work. Plus, you need sufficient funds to live on (I usually recommend an additional $25,000 to $50,000). Your focus on the proportionality test is misplaces ... the substantiality and marginality tests are the appropriate ones to consider. Talk to an attorney, many of us use Skype.

E-2 rules and regulations are quite complex, byzantine, contradictory at times and anything but confusing to the layperson. Especially when you have so much at stake, don't attempt to go it alone. Work with a qualified immigration lawyer who has a proven track record in successfully filing E-2 visa applications. Don't attempt to go it alone. As a specific example to you, kindly be advised that US consulates worldwide take, on average, 8 to 14 weeks to "digest" an E-2 visa application package once received, since each of these applications is the "most difficult and complex" type of visa applications the consular staff has to deal with. (Note that the words I have under " " quotations are a direct repetition of the opinion of a US consul general during an immigration law seminar not too long ago..

Basically the amount of qualifying funds invested in the US, should exceed the cost of establishing such business. You have not clarified what business you are investing in or creating - if there are any non-monetary contributions, for example IP, Specialized knowledge, etc. Depending upon business, $100K may or may not be substantial and may not meet proportionality test. Its pointless to ask this question without disclosing facts. Proceed through an attorney.

In a startup business, the proportionality test is basically a comparison or how much you invested to what is required to normally start the business. As my colleagues have noted, E-2 visa regulations and adjudications are quite complex. You will do yourself well by consulting with an experienced immigration attorney who can review your investment to determine it's E-2 visa qualifications before you get stuck with something your cannot operate.