StackSocial offers downloads of Clip Studio Paint Pro for PC and Mac for $29.99. Coupon code "DN25" cuts that to $22.50. With free shipping, that's the lowest price we could find by $27. The successor to Manga Studio, this software allows you to create manga and comics with drawing tools, filters, and special effects.
With these companies, it might be easier than you think to negotiate your monthly bill down.