Government charges differ between a port-of-entry application and a USCIS I-129 petition; check the current amounts in the USCIS fee schedule (G-1055) and the CBP fee rather than relying on a figure from a colleague. Employer and applicant should agree in writing who pays each item.
Separate government fees from everything else
Build the estimate in three columns. First, government charges: the port-of-entry TN fee collected by CBP, or the I-129 filing fee and any optional premium processing fee if the employer files with USCIS; each TD family member has their own admission or application fee. Second, evidence costs: certified transcripts, credential descriptions, courier charges and any translation.
Third, professional fees for preparing the letter and reviewing the file. Employer policies vary; some distributors will fund the petition and professional fees but expect the applicant to pay family and travel costs. Confirm this in the offer letter so the arrangement does not become a dispute later.
Do not forget the state side: if the role touches engineering sign-off, licensing or exam costs may arise, and those are professional-practice expenses rather than immigration expenses. Verify the amounts on the official fee schedule on the day the budget is finalized.