Cheap Calculus III Courses?

So I’m in a predicament. I need to take a math course my senior year since I finished AP Calculus BC junior year. The problem: All of the good online Calculus III courses offered by vendors such as University of Illinois NetMath or University of North Dakota cost over $1000. My school is willing to pay for 50% but that would leave my parents with a +$500 bill.

Are there any cheaper alternatives? Originally I tried to register for a course at my local community college but they only let dual enrollment high school students take up to Calculus II. What should I do? Should I keep pestering my local community college until they let me take the course, or should I suck it up and spend the $500 for the University of North Dakota course?

$500 is a very reasonable price for a year of college credit. We are paying $500 each semester for my daughter to take that course even though it is offered in our HS with a teacher who has HS and college teaching credentials. Well; she could take it free but to get the college credit and transcript from the college involved we have to pay. It’s better to have the 4 year college credit anyway as some of the more selective schools won’t accept transfer credit from 2 year schools.