In my opinion, IEO is not for crypto startups that are seeking funds to kick start their project but for projects that have raised capital already or have rich advisor and team to fund the project. Fund-raising through IEO can be very challenging for startups that need money to kickstart their project, because they will need large amount of money to conduct their tokensale on good exchanges, as this exchanges only list projects that meet their legal requirements and can also afford to pay their listing fees. So the best means to raise money or capital for new projects is to present their proposal to Venture capital firms or Angel investors.
if we don't know about how much exchange site was charging for ICO to listed and become IEO we can't create a lot of assumption about that. But that's indeed and i just consider the listing fees on binance which around 5 million dollars and with IEO binance maybe charge even more than it. But i never saw a real mechanism that already used exchange site about how its listing works.
An ico like bcnex has already done to get the funds from angel but that platform still tries to get more finds through ICO mechanism.