Global IP Asset

My company owns a fossil fuel replacement technology for transport. Our lawyers deem the IP to be the basis for a global utility but cannot find a corporate financier to value it. We have daily approaches from investors who tell us that the IP is worth very little but they want it and they need control. One of the 'Big Four' has taken an interest and asked us to produce the 'numbers' for operation at a global level. This put the IP value at $2.7Tn. After this they said we need to be more reasonable and look at a sub $10M value (!). I need advice here. The technology is independently verified and tested. It can provide an electric car with 1500 miles range for 10 cents a mile and has zero emissions (well-to-wheels). Please advise.