The government charge is the admission processing fee at the port of entry, paid once for the admission period rather than per trip, or the USCIS Form I-129 fee if the employer petitions. Travel, accommodation and field equipment are contract matters between the forester and the company.
Fees follow admissions, not journeys
Because TN admission is granted for a period, the immigration charge is incurred when that admission is granted and not each time she crosses afterwards. If the U.S. company chooses to file Form I-129 with USCIS instead, the petition fee and any optional premium-processing charge are set by the published fee schedule, Form G-1055, and should be read there rather than taken from a quoted figure.
Everything else in a seasonal forestry engagement is commercial. Who pays for flights to the block, for accommodation in a work camp, for safety gear and for the vehicle should be settled in the retainer, because those amounts are far larger over a year than the immigration fees. A separate item worth agreeing in writing is what happens if an admission is refused: whether the company holds the assignment, and who bears the cost of the wasted trip.
Hypothetical example: a Hope urban planner receives a three-year offer and the employer proposes to reimburse her only after the first project invoice clears. A first review produces a cost list divided into immigration charges, travel, and professional expenses, with the written offer settling who bears each item. She should also ask whether a failed admission changes the reimbursement promise, because an informal assurance from a project manager may not bind the company.
The important decision is whether to incur non-refundable travel and accommodation costs before the documentation has been reviewed.