The most low-cost I know of with widest reach (most countries) is https://www.adyen.com/pricing
Because you can choose which processor you want to use and there are many low-cost ones, including some inter-bank ones with fixed cost (no %)
Most shops like WooCommerce and Shopify have ready-to-use plugins for it.
(I'm not affiliated, but i build e-commerce for brands)
On a related note, you can look at hyperswitch [1], which is an open-source payment orchestrator that supports multiple payment processors. You can self-host it or they have a hosted version as well.
1. https://github.com/juspay/hyperswitch
(not affiliated with this project in any way)