Next time, ask first and then buy 
TBH the rig isn't that bad for the money. Most of us on here will baulk at the price tag, since that rig should really be a lot closer to £600 or less if you just count components... but then we're also willing to put a lot of hours into it to get what we want - you're paying for those hours of research and work.
If I'd spent £150 getting someone else to build it (and then had the warranty so they'd maintain it for 3 years), and then spent the 30+ hours at work/freelancing rather than at home tinkering with my rig (plus all the research!), I would have made a lot of money. On the other hand, I do this as a hobby, so I got something else out of my time - if you don't feel confident enough with a set of cables to do it yourself, you weren't ripped off.
In short:
Yes, we could have gotten you a better deal - no you weren't robbed blind, although that price is pushing it.

TBH the rig isn't that bad for the money. Most of us on here will baulk at the price tag, since that rig should really be a lot closer to £600 or less if you just count components... but then we're also willing to put a lot of hours into it to get what we want - you're paying for those hours of research and work.
If I'd spent £150 getting someone else to build it (and then had the warranty so they'd maintain it for 3 years), and then spent the 30+ hours at work/freelancing rather than at home tinkering with my rig (plus all the research!), I would have made a lot of money. On the other hand, I do this as a hobby, so I got something else out of my time - if you don't feel confident enough with a set of cables to do it yourself, you weren't ripped off.
In short:
Yes, we could have gotten you a better deal - no you weren't robbed blind, although that price is pushing it.