The other thing to think about when deciding to scan bio is the value of systems you don't visit because you spent 15/20 (or more if it's hard to find) minutes scanning bacteria worth 5m credits. You can jump through and FSS 5 or 6 systems in that time and you can make up your 5m credits that way in carto data, and you might be lucky and find a hi value bio or ELW/WW while traveling and you have already well exceeded any value you earned from the bacteria. In general I don't scan bacteria, unless it's a new find in the region and I don't land on planets that have already been walked on.
But as Greasetrap42 says, money becomes irrelevant eventually, I now rarely travel more than 30kls in system even for high value bio because exploring new systems is my thing, we all need to decide our own methods and make our own decisions. You've had some advice here, the most important is getting some tools to help you identify what's there, like Elite Observatory, so you should be able to decide for yourself what you want to do, but the most important thing is, do what you enjoy, and if that's scanning bacteria go right ahead, someones got to do it
