I think it is misleading to be overconcerned with the relative transfer costs, since they are all in the same ballpark. The unaddressed bigger problem is signing up with the wrong broker. Some possible examples:

You have a cheap broker, but find you don't qualify for the cheap rates (account size or trading frequency).

You are making regular contributions, and would rather have a robo-adviser handle the repeated investing automatically instead of doing it manually.

Your regular contributions are costing a lot in trading fees, and you want to move to a broker who waives fees for ETF purchases.

You broker waives fees for ETF purchases, but has minimum purchase requirements you can't meet, or does not offer it for ETFs you want to purchase.

You like certain index mutual funds, but they are proprietary to a different bank-based broker.