An interesting way to buy themes was implemented on ThemeSnap: you can buy a sort of club subscription which gives you access to all themes of a specific author. After that a (relatively) small monthly subscription fee is required to renew your subscription and maintain access to all author’s themes.
I’ll mention in this article a few authors which I think that have worthy club subscriptions.
He has 12 Drupal Themes in his portfolio in the $49 – $79 price range. He has themes for online portfolios, real estate, digital agencies, car dealers, job boards / portals, awesome multipurpose themes, ecommerce, for online magazines, etc.
His subscription is $599, which means that you get all his items for a $49/theme average price. Subscription renewal fee (after the first month, as the first month is free) is $19.
Another worthy of mentioning Drupal themes author is ThemeSnap. They’ve got 23 Drupal Themes in their club subscription. They have several Classified Ads Drupal themes, video Drupal themes, online magazine style, questions and answers, Pinterest like with advanced functionality, ecommerce, etc. Prices vary between $29 and $119 per theme.
An important mention here would be the fact that besides PayPal, you can purchase these club subscriptions via Stripe using your credit/debit card.