Nae vegan shoes has difderent price range shoes. Well not sure if all of them are sustainably & ethically made, but you can find many shoes which are considered sustainable.
Talking about the price…. You already can find many high street fashion brands offering conscious products.
If you are a small brand and take all of the steps to make not just the product sustainable, but all the process like energy, ethical and fair wages, sustainable made ( grown) materials, not high quantities, the product becomes expensive.
While you are in UK you can find more sustainable and affordable brands for example using platform Wolfandbadger.com they have quite a few UK based companies as well from all around (it is useful tool, but sometimes buying direct is cheaper).
As well I believe brands like Cariuma has shops in UK (even it is Brazilian company, but they are just simple one of the best sneakers companies).
But so totally support the idea that any kind of sustainable items should be affordable.
About fast fashion & sustainability, well of course it is better to buy sustainable, but what is behind it? If they just use sustainable fabrics, but there is no consideration about the process maybe it is still not enough.
P.s. anyway it is still a business! Everyone wants to earn! Everlane has quite an interesting charts with the prices for different processes.