What’s the fee for converting a 401k to a self directed IRA?

"$250 or more" per https://www.nerdwallet.com/article/investing/self-...

There should not be any fee to convert that as long as you have left employment with the past employer that had tehe 401k with.

I converted, there was no fee. BUT, I kept it in the same company. 

There is no fee if you do it correctly, and use a reputable company. I recommend Vanguard for your IRA. They have the lowest fees in the industry. Call up Vanguard and ask them to help you do the roll over correctly. If done incorrectly, there are taxes and penalties.

Depends on the custodian. Sometimes there's a fee on both sides.