I agree. Until recently they were literally paying users to open an account and recruit new customers. You could exchange up to £5000/month for free (now only £1000). And if you need to make a big single transfer, for instance while moving to a different country, paying one year of premium membership can still be cheaper than Transferwise's fee on that single transaction.
Margin compression is a thing for banks who haven't realized yet they're software companies that offer financial services now, and the moat continues to shrink (getting a banking license is hard, partnering with another bank in need of deposits less so). One must be willing to cannibalize margins to survive or be prepared to be left behind by those who are more efficient (and I admit that macro trends make this harder than in the past; "borrow at 3, lend at 6, at the golf course by 3" [1] is dead).
Disclosure: Part of my work is helping old banks attempt to turn into software companies, with wildly varying results depending on the org.