Stock brokers be it bank or pure broker also carry costs directly from stock exchanges themselves. There's always costs, while maybe some banks might sunk some of the costs if you are using their other services. Haven't really looked into it as at least 10 years ago stock trading was so cumbersome with banks for an individual.

Institutional and people with larger portfolios usually pay flat fee and others usually percentage cut and/or combination of these.

Nordnet (unfortunately you need google translate for the pricing) is by far the biggest in Finland for trading and have worked great for me some 15 years. Some good analytics to follow and easy to use.