Forestry is an activity that was introduced in Farming Simulator 15. It offers a quick, large profit, but can be more labor intensive because you cannot hire a worker to help.
The cost of trees is $7,000 on normal. But the profits per tree vary greatly from about a 50% loss ($3,500 selling price on hard) to a 65% profit ($11,500 selling price on easy). From indications easy can net you over $100,000 for a tree to hard where you can barely get a profit at all buying trees to harvest.