For higher resolution you should seriously consider charging a subscription, or on a pay-for-credits basis. Many organizations, especially those with limited or highly-demanded in-house design talent (ranging from finance to marketing to funded startups), would absolutely justify this product at rates absurdly greater than server costs. Unlike Fivver talent manually tracing boundaries, this has near instant turnaround, and that is HUGE for people with deadlines and infinite Uber budgets who just need stock images combined together.

Source: am in NYC.