The Constitution tells us who can/can't vote. Voting itself and the right to vote is assumed in the very fabric of the government it establishes. If you are affected by the laws of the land, you have a say in what those laws are. Period. Doesn't matter if you're smart, or wealthy, or white or even born here so long as you've been naturalized.
Poll taxes have been ruled unconstitutional by the Supreme Court, so you can't charge for the right to vote these days. Voting cannot cost money.
The Constitution tells us our right to bear arms in order to have a well regulated militia will not be infringed.
No one has ever expected those firearms to be free. They weren't free then and they aren't free now. The Supreme Court has never overturned fees associated with licensing guns or performing background checks, and I'm sure the NRA has tried, so it is okay to have charges associated with gun ownership.
The two rights you are trying to compare are not actually the same. Without voting, our government would not exist. Without guns in every cupboard and glovebox, I believe our country would function quite well. One is essential to government. The other is not.