If you know where to get that shock for £400, please let me know. I've been seeing prices that are at least twice that.
That price is probably right for the model, I only took the cost of their cheapest rear motorcycle shock just to make a point that even their "worst" one is double the cost of most good ones and a hefty chunk of money.
Most people try to replicate these builds on a shoestring budget and give up when they realise how much work/$$$ is needed.