With so many variables in applications I believe you will find, as zdas04 and BNiessing have indicated, historical data based on application may be the best baseline. Of course, economic climate will significantly impact just about everything.
If you are dealing with production pre-engineered applications you may be able to develop a power or capacity correlation to price. Introducing engineering into the equation and supplier backlog provides for the scenarios already posted – market forces shall prevail.
In previous a life previous life in Applications for an OEM I worked with several end users to develop price scales for specific processes. Depending on the application you may find that not all OEMs/packagers are equal – in price and of course quality. It was rare, if ever, that a best fit throughout a large range is available from a sole source, but it is possible. Your task may fit the products of brand X like a glove, or the process may be able to be adjusted to a cost effective product.
Good luck.