The “blue” ones cost 16, the others 32 to 64, but the enemies drop more bits (up to 8) as you progress so by the ending you should be able to complete, or close to, one of the skill branches. I am making them selectable in the new version to show the details.
Maybe I can do the opposite, rebuild the 7DRL version as standalone and update the browser version, github should have everything I need. I will post a reply here, in case you are still interested, when ready in the weekend. It’s still pretty challenging, but more fair, I guess :)