How much does it cost to buy cryptocurrency on Coinbase?

I'm curious about the cost involved in purchasing cryptocurrency through Coinbase. Could you elaborate on the various fees and charges that one might encounter when making a purchase? Is there a flat fee or is it based on the amount being transacted? Additionally, are there any hidden costs or charges that buyers should be aware of before making a transaction? Clarifying these points would greatly assist potential investors in making informed decisions about their purchases on Coinbase.