Update from Fortunejack, they have lowered the minimum withdrawal from $150 to $50.
As the consequence, withdrawal fee is charged for withdrawal between $50-$150, fixed $4 fee for btc & eth and $1 for other currencies.
While withdrawal above $150 is still free of withdrawal fee.
Thanks for the update. The $150 minimum was quite high, which put FortuneJack on the list of crypto casinos with the highest minimum withdrawal amounts. The $50 looks much better now, and puts them further down on the list. Too bad that all withdrawals aren't free of charge, but I understand their decision, especially now when the network fees are crazy high.
I have read their blog post they linked to in their ANN, but it doesn't explain properly the fixed fee rates you mentioned. I will have to log into my account tomorrow and check it myself just to be 100% sure.