Hey there,
Is your $2,700 calculation just for one class? If so, I think that is high (unless you're including gas money into that equation - I'm not sure how far you are from campus). I took a 3-credit, 400-level Bio class at GMU this past fall. I also had to apply as a non-degree student (I think that was $70, like you said). The cost of the actual class was $1,133.25 (~$378/credit) and then there was a $60 Non-Degree Educational Resource Fee. In addition, I paid ~$170 for parking for the semester (I chose to park in the garage right next to the building because it was my cheapest and most convenient option). My parking and fuel costs were pretty reasonable because I chose a class that had longer lectures but only met once per week, so that helped a lot. Fuel might have cost me ~$100 for the semester (Leesburg -> Fairfax, 60mi/wk). I also didn't have to purchase a textbook. In total, the endeavor ran me ~$1,534. I hope that helps, and good luck! I also had my heart set on VMRCVM this year so I really do feel your pain!
The kicker (aka my rant):
In my file review last year, VMRCVM told me to take a class, "any class", that would help raise my last 45 GPA. Rather than taking a random/easy class, I chose to take a challenging 400-level Bio class on Vaccines & Immunology thinking it would show some dedication and give me an introduction to those topics for vet school. I shelled out over $1,500 to take that class and bring my last 45 GPA to a 3.6 and still haven't been offered an interview at VMRCVM, which is now my in-state school. I very well may have to reapply again next year (since they hold their interviews in one week and the only other school I have to hear from is Oklahoma OOS), which means I should retake the Organic Chem series (another ~$3,000+ down the tubes) and probably the GRE again. When you count the costs of taking these classes, changing my driver's license/registration to become a VA resident, two failed application cycles and the possible cost of a third, I will have spent over $7,000 out of pocket trying to get into vet school (nevermind my $60k worth of undergrad debt). Sometimes, I question my sanity