The simple answer to this question is that the prices on Robinhood and Coinbase are different because they are two different exchanges. However, there is a bit more to it than that.
Coinbase is a regulated exchange, which means that it has to comply with certain rules and regulations. This includes things like KYC (know your customer) and AML (anti money laundering) guidelines.
Robinhood is not a regulated exchange, which means that it does not have to comply with these same rules and regulations.
This difference in regulation means that Coinbase is able to offer a wider range of services than Robinhood. For example, Coinbase allows users to buy and sell cryptocurrencies, as well as store them in a wallet on the Coinbase platform.
Robinhood only allows users to buy and sell cryptocurrencies; it does not offer a wallet service.
The difference in regulation also affects the fees that each exchange charges. Coinbase charges higher fees than Robinhood because it has more costs associated with its compliance with regulatory requirements.
The bottom line is that the prices on Robinhood and Coinbase are different because they are two different exchanges with different levels of regulation. One is a regulated exchange and the other is not, which affects the services that each exchange can offer and the fees that they charge.