You have to include the costs of conversion - gas power plant. Also you have some some losses during conversion from heat to electricity, a modern gas power plant can be up to 60% efficient.

https://en.wikipedia.org/wiki/Gas-fired_power_plant

Then you have electric distribution costs (costs for building and maintenance of electric grid, transformers, power lines).

In many industrial process heat applications direct burning of gas is preferred, because it lowers the costs.