Maybe I'm not understanding you properly; correct my mistakes:
You have 1800 magazines for which you're going to sell subscriptions. Each magazine has a different per-year subscription price. You wish to bill people for the number of years they choose times the subscription price of the magazine to which they are subscribing.
My solution would be to make each magazine a "product", make the per-year subscription price the "price" and make years the "quantity".
Please provide info on where I've misunderstood, and what you're trying to properly accomplish.