Is that some sort of legacy pricing? because on https://chatgpt.com/pricing/?type=team I see an option of either £15/ month or £75/ month, per seat, 2 seats required. So it's more expensive than a single £89/ month pro subscription.
How is 2 x 15 more expensive than 89?
The 2x15 is not ChatGPT Pro you're getting, it's the equivalent of the "Plus" plan. So yes, you can get 2 "Plus" subscriptions for more money than it would cost to get them as a personal ones.
The 2 x 15 gets you the permission to use Claude at API rates, it comes with no or minimal usage.