This is a question I've had and pondered for many many years now. 7 years ago now (wow really?) whilst I was at university I came across a problem which I had, and which all my fellow students had too.
This idea progressed in my mind and developed into something which I saw was really a huge problem for everyone nationwide, indeed worldwide, and one which I then set out to resolve.
I had taught myself HTML/CSS back in the days of web 1.0 as a 12 year old, but this wasn't something I kept up with since I was 17 and I was now 20 yrs old, and the industry and technology had EXPLODED and changed beyond all recognition.
At the time 7 yrs ago I'd say my idea was well ahead of the capability of technology back then, and my site would've cost maybe £50-60k given the functionality I had wanted and would've still been pretty basic. Nowadays based on estimates it seems I can get close to the required functionality (variable on finish) for between about 10% and 20% of this cost.
Whilst I was at university I tried picking up the web dev skills again, and hashed together a really poor effort at a website for my new business, which I genuinely laboured over for about 3 weeks. I then went and pitched to a local company.
The poor women who recieved my pitch must've felt pity for me more than anything else, and whilst she agreed my concept was where the market was headed, she said my execution needed 'a bit of refinement' - I love the British sense of politeness but really in hindsight a slap round my face and a 'seriously this is pathetic, you have a decent idea, but get it built properly!' would've been much more useful...
Now, back then I had a living budget of about £20 a week to do food, travel & anyhting else I needed, but I had this burning hole in my brain which kept telling me this idea was worth pursuing, so I went about developing it myself. Over the proceeding years I've genuinely spent more time and effort on trying to put the site together myself, rather than even contemplating paying for it.
Whilst I made the best with the resources I had at the time, I did learn about how important it is to reduce costs down as much as possible.
I've learnt a lot about what is possible with the tech available, and when having discussions with developers and freelancers I've now become able to spot the guys who don't know what they're doing vs those who do, and I've developed skills in how to cost up the project. I'm able to have serious discussions with developers about what I want, and how I see the infrastucture working.
What I have still to get out of the mindset is that:
a) my time costs and therefore I shouldn't be happy spending so much of my time on something that will be poor quality,
b) whilst I understand how the script/technology works from a technical point of view and can challenge/assist developers on the sites methodology, I'm not capable in executing it properly
c) I have the basic understanding of how to set up a site and use templates to make it semi decent, but a professional will take the idea and make it work, and this is what you pay the additional amount for.
This is a hard mindset to get out of, because I'm very much self sufficient, and will try and put in elbow grease to get something done if I can do it myself vs paying for it, but I'm now beginning to realise that my unwillingness to actually pay for the development of my site has not only meant that I don't have the site I need right now, but also I might have missed out on the potential to be a market leader and I might now be in a situation where I can't afford to compete because what I have is perhaps not as revolutionary as it would've been back then.
However, I also think perhaps there is still a chance, but I don't know how to justify spending the sorts of cash I need to in order to get it off the ground given the level of technological competition now compared to 7-8 years ago... Since then I've seen companies come up and become national multi multi million pound businesses based on lesser technology than I was trying to build in my bedroom years ago, and if I'd been savvy enough to find a way to fund it, or been less stubborn, worried about the idea being stolen, and indeed proud of my ability to develop basic sites, it might've been my business that has gotten there.
Hence why even now, the site I've recently tried to put together for my business is more shaped by my capability than what I actually want it to be.
The dilemma continues for me unfortunately!
TL

R - I thought I could do it myself, turns out I can't, if I'd had the cash I still wouldn't have hired someone, but probably should've, and now as a result I'm probably not going to be able to be the revolutionary success story I thought I should've been, because it's not so much of a stretch for an already existing market leader to implement the same idea, and I'm still trying to do things on the cheap to the detriment of the idea, and more importantly MY ability to implement it as a business idea in the current technological environment.
As a result I think if you have an idea, it's worth paying for it if you believe in it, as the unwillingness to have it done properly can be life changing, and you could be like me looking back and thinking 'well if only I had...?'
In answer to the question - yes it's important to drive down the web development cost, but you might lose out on many opportunities in the process of trying to make do with lesser.