It depends on all of your current financial circumstances and how much debt you have. As such, there is no specific dollar figure which makes you ineligible for the services of a Public Defender. For example, individuals who are in custody and are unable to post bail are presumed to be eligible for Public Defender services. On the other hand, if they can afford to post a large amount for bail, or own a home, they might not be eligible. If they have enough financial assets to afford private counsel, they are not eligible to be represented by a Public Defender.
Regardless of whether a defendant is in custody or out of custody, all of that person's financial obligations (such as the need to support a family, pre-existing debts, rent/mortgage, etc.), are balanced against assets and income, including community property income, in determining whether that person can afford to hire private counsel.