Typically, different share classes reflect different expense ratios depending on initial investment amount, load or transaction fee, or association of some form, like certain 401K plans. (mutualfundobserver.com)
I understand that different ETFs may cost different amounts of money per share, as you are buying a proportional amount of each company on the index, but why can two ETFs that cost roughly the same amount of money per share but have different expense ratios coexist i.e. why would someone be prepared to pay more for the same thing? (money.stackexchange.com)
There are different expense ratios for different funds. (blog.roboadviso.com)