The cost to the victim. Someone grabs a few unsecured tie downs off a truck at a truck stop that's a hundred bucks. Someone scraps some spools of copper stolen from a job site and it could be thousands.

I think having a step function where you define all theft below a dollar amount as one type and then above as a different type is just legacy code from back in the day when it wasn't reasonable for the legislature to just say "the fine will be X-times the replacement cost of the goods or an equivalent jail time as determined by table Y in appendix Z" and expect the courts to be able to enforce it in an efficient enough manner.

The fact that we we have basically two classes of crime that include both violent and nonviolent crime results in a lot of overlap where you can have some pretty bad misdemeanors and some pretty mild felonies all depending on legal technicalities.