MLB offers a ticket to all 2017 Oakland Athletic Home Games for $19.99 per month plus a $5 service fee. That's up to $200 less than what you'd pay buying a ticket for each game separately. You can access your tickets from the MLB.com Ballpark App for iOS or Android.
Note: This subscription will auto-renew each month at $19.99. However, you may cancel your subscription before the 20th of any month to avoid the next months' charge.