So to preface: I am barred (inactive) in Mass, but I don't practice criminal law there so treat this like I'm a layperson. I do practice criminal defense and was a prosecutor in California, and they have a similar rule, so I'll just answer based on the laws there.

That's pretty much correct, at least in CA. The way it works in CA is if bail is set, it must be at a level that's affordable to the individual (ie not set on a schedule sheet) but still be an incentive to return to court. There can be additional requirements for bail like an ankle monitor, but that's not always needed. However, as you mentioned, depending on the severity of the crime, there's a strong possibility that bail will just not be set. Like robbery, for example, which is a violent crime (and counts as a 'strike' for CA sentencing purposes). It's very serious and so the judge may decide that the danger to the community and the risk of flight outweighs the accused's right to bail. They weigh a number of factors, but they're also basing the seriousness on how the DA charged the case, not on a hearing with evidence presented. For example, I have a client right now accused of a very serious crime and was given no bail, but the violent crime he's charged with was done in self-defense, which isn't in the police report or the complaint, so the judge can't really consider it.

So simply put, the judge first determines SHOULD they get bail, and then determines how much based on their income/resources.