Valuation of a company is not cut and dry as to market value.
There is a lot to take into consideration, most importantly potential unrealized revenue, and more importantly in this case relationships and connections.
Sigma Labs close ties with GE, Honeywell, Los Alamos National Lab and America Makes alone may be worth far more than $70M to a potential buyer. So lets also be realistic about that.
Connections are everything in the Aerospace, Medical, and other big money industries.