The short answer is, whatever the going rate in your area is. Timber prices can vary by region, you will need to investigate what the going rate is in your area. Start by determining local rough cut lumber prices.
Call sawmills around you and find out prices for all grades of lumber, ignore the highest and lowest prices and take an average of all the other mills prices and you will have a good idea of the going rate for lumber. Then all you need to do is figure out what it costs you to harvest the timber and saw it into lumber. Take the average lumber price and subtract the costs, and profits, then you have an approximate figure the timber prices you can pay.
You will also need to consider other factors such as accessibility. Is the piece of timber on low ground where it is wet most of the year? Are all the trees on the side of a steep hill? Is there a place to set up a landing that is high and dry? You will need to be able to get trucks in and out without getting stuck. How far is the timber from the landing. Is your skidding trail is a mile long? How far do the logs need to be shipped once they are harvested? All of these questions need to be answered before you can submit your bid.
You may find yourself outbid even at the high end of your scale. There are many different factors involved, and every piece of timber is different. Timber prices can vary greatly depending on the quality of the trees. You will have to pay a premium for timber that has a lot of high quality grade and veneer material. Timber that is low quality and is made up of mostly pallet grade logs will be at the lower end of the scale.