I think that the rough numbers that you are after are of the order of:
- Steam turbine generator plant, price inclusive of steam plant, generator, turbine, fuel system, auxiliaries, electrical equipment (including transformers) and installation - order of magnitude somewhere around $800 - $1000/kW
- Power transformer equipment cost - somewhere around $12-$15/kVA, for medium voltage units
Doesn't seem like much of an equation, until you consider the possible payback of a generation plant. Most cogeneration schemes that I have been involved in offer a simple payback of between 1 and 3 years, depending on utility and fuel costs.