How do you avoid underestimating the expenses associated with cloud migration?

Understand the hidden costs like upskilling, data transfer costs and eventually knowing that not investing in people can have a bad impact later

go read on TBM Technology Business Management and find a company specialising in technology costing to help - www.tbmcouncil.org may help - i have no affiliation with them, just know this group exists.

You really need solid understanding of your full total cost of ownership (TCO) of existing costs including all software licensing

You may be surprised by new costs for software that is installed in the Cloud under totally different terms and conditions

And spend time understanding billing for traffic in and out of the Cloud

And don’t oversize your cloud configuration. Too many architects design for estimated demand that never comes or is far into the future. Size for what you need now. You can grow larger later.

There will still be more surprises… DR costs are different, backups are different…. Don’t rush, plan, plan, plan