Cost of ISO 27001 certification and Internal auditor re-certification

Here are the answers:

I am trying to estimate the cost for ISO 27001 certification with my company

Answer: The cost of certification depends on the size of your company (i.e. the number of employees) and the price per man/day of local certification bodies - the best thing is to ask for quotes from a couple of certification bodies to get a feeling for the price. Here's an article that can help you: How to choose a certification body https://advisera.com/blog/2021/01/11/how-to-choose-an-iso-certification-body/

The cost of implementation of a standard will include several items, you can find the details here: How much does ISO 27001 implementation cost? https://advisera.com/27001academy/blog/2011/02/08/how-much-does-iso-27001-implementation-cost/

I am trying to figure out for Internal auditor certification is there a requirement that auditors get recertified periodically?

There is no requirement for periodic certification (or maintenance) of internal audit certification - once you get the certificate, it is valid indefinitely. Here you can find online ISO 27001 Internal Auditor Course with possibility of certification: https://advisera.com/training/iso-27001-internal-auditor-course/