A 3.75% of the cars total value as a "document fee" is the same as a 3.75% sales tax. The only difference is that you also pay it when you bring in a car from out of state.
Actually where I live, tax would be $0.06. Registration would be around $300 (guessing). There would be a few other fees and then a boatload for insurance, but not $50k. But I get what you're saying.