Going to be tough for that competitor to survive if they don't pivot from a 'Stripe-clone'. Hope they're well funded and well backed.
You need to do a huge volume of transactions to be able to live off 2.6% + 30c, close to two million a month to support a startup with 5 fully loaded employees including the founders.
Working with a lot of Ecommerce sites I know a well established one (attached to 3 bricks and mortar stores) does on average $16k a month. Say on average an Online store is doing 10k/month you're looking at 200 clients to keep the payment processor afloat. Doable but you'd want them to have some runway otherwise people are gonna go with Stripe to know they've got a payment gateway that's not gonna disappear