std::regex is much slower than boost::regex on VC2015U3

std::wregex EXCEL_CELL_REGEX(L"=\"(.*)\"", std::regex::optimize);
std::wstring text = L"=\"300498\"";
for (int i = 0; i < 981 * 6; i++) {
    std::wsmatch match;
    std::regex_match(text, match, EXCEL_CELL_REGEX);
}

Above code takes about 9 seconds

boost::wregex EXCEL_CELL_REGEX(L"=\"(.*)\"", boost::regex::optimize);
std::wstring text = L"=\"300498\"";
for (int i = 0; i < 981 * 6; i++) {
    boost::wsmatch match;
    boost::regex_match(text, match, EXCEL_CELL_REGEX);
}

Above code takes about 1.5 seconds

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Those tests are built on Debug configuration.

Do you know why std::regex is so slow? How to optimize the code?