It may also be impacted by the cost of installing the QMS, separate from salaries, etc. If there are things the standard requires that you're not doing now (e.g., calibration) you may need to expend funds to acquire items (e.g., calibration standards and/or services). There are also funds for external training for auditors, etc., unless you do this in-house.
The in-house cost (if you include labor hours) is by far more than the cost of the registration audit & certificate, although most is absorbed cost since you're already paying the people who will do the documentation, etc. You may also incur costs for consultants, if you choose to use them.
And although the costs vary widely I would estimate your cost for the initial registration audit would be somewhere around $20k-$25k (review of quality manual, live audit, travel expenses). If you have a pre-assessment it would be additional. Some registrars will also hit you for travel time, for certificate itself, etc.
Then you will have the surveillance audits (typically every 6 months) which will run another $5k-10k.