你怎麽會信chatGPT的一本正經胡說八道，而不信網友。帳戶上都說了是institutional SP index，見內

看這兩個links

https://institutional.vanguard.com/investments/product-details/fund/2040 這是機構買的SP500 index，費用比Vfiax低

https://investor.vanguard.com/investment-products/mutual-funds/profile/vgxrx#