Since many indexes are weighted by price, I find myself wondering if index fund investing has an element of "buy high, sell low" to it. Only if you buy shares

Since many indexes are weighted by price, I find myself wondering if index fund investing has an element of "buy high, sell low" to it. Only if you buy shares of the fund when they are high, and sell when they are low. An index fund that buys a set of stocks in proportion to market price at one point in time will automatically capture the relative gains and losses within that set. If Apple's share price doubles, then the market value of its shares that the fund owns will also double, and it will occupy a relatively greater percentage of the fund's portfolio. Companies with a flat or declining share price will account for a relatively lesser percentage over time. Some buying and selling needs to happen, to accommodate new investors and to handle turnover within the target index, but the point of passive index funds is that you don't need trades to capture market performance.