Ohhh, I was just looking at upgrading to the Explore this morning, good question. It says on the website that the subscription starts at $7.99. What would you need to upgrade it for? What's not included in the base $7.99 one?
The difference in the price is you can pay a one time fee of $95.88 for one year (which comes to $7.99 a month) or just pay $9.99 each month. Both get you the same access but if you pay for a year in advance, you'll save $24!