There is no pre-defined range or difference which tells you whether the two values are quite different. You have to use your own judgement and knowledge of the data to decide.
Having said that, your AUROC is relatively good (>90), however your PRAUC is not (<50), which tells you that you did not effectively model the imbalance in your data. In other words, most of the good predictions were in the majority class.
If you had dealt with the imbalance in your data, your model would return similar AUROC and PRAUC values. The difference between 90 and 50 is significant.
For a clearer picture of what is going on try using a more easily interpretable measure such as accuracy, F1, and so on (despite their shortcomings), this will tell you quickly where the issues are.