Many parents would say more studies equal to more income, however I would say they are not always equal. On the other hand, they have a relationship.
If you think you can earn a lots of money for sure after you study, then you might disappointed by yourself, dont forget you have a lots of classmate who study beside you as well.
If you think you can keep earning $30000+ now and or more in the future for sure, you might also disappointed yourself as well because nothing is grauanteed. You will have nothing once your lost this job, no matter money or time for study.
What you can believe is, if someone will offer a good job at this moment, and I dont think you cannot have another better or same offer after your finished your study as long as you try your best in your study. Why would a boss not gonna to offer a job to a person who is improved or upgraded few years later? I can only find a reason is that working feild is no longer in good will or decrease of demand. In this case, the different between you give up the job and go study now or you give up your study to stick with this job is ONLY you have some money in saving or you have a degree in your hand. So this is very clearly for you to make your choice!
Remember study wont make money for you but it can help you to improve your sight and mind, and these things will stay with you in the rest of your life, no one can take it away from you. You are the one to handle a job and make money for yourself, not the job who make you earn money!