Cryptocurrency exchanges are direct-to-retail so anyone can run HFT strategies and act as a market maker. Thus, cryptocurrency trading is “more democratized.”
On the order of thousands of dollars a month[0], depending on how close you want to get.
[0]: https://www.cmegroup.com/globex/connectivity-options.html
With no stance on whether people should be doing HFT as a hobby, presumably there is a finite amount of colocation space available and an opportunity cost/maintenance associated with onboarding people so this is what the market and regulators decided were the table stakes?
Cryptocurrency exchanges are like many FX exchanges. They are not exchanges like the regulated stock, futures and options exchanges are, but are more like decentralized trading pools with unsynchronized order books, which are opaquely operated by a single broker. In crypto exchanges, it is not that there is no broker, but that the exchange and the broker are the same entity. There is no standardized protocol to route independently managed orders directly to crypto exchange servers. There's usually no way to directly interact with the exchange server at all.