Jennifer and I were missing blinds for our house, and some kind of closet solution (right now, we only have empty closets, and nowhere to put our stuff away).
For the blinds, the least expensive was actually to get premium hunter douglas material direct from blinds.com, and tack on a local installer. It was cheaper and better than Home Depot, or 3 day blinds (this is the summary of several days of work and research from Jennifer).

For closets, to have a good idea of what we needed and designed, you can look at what we got after working with Coast Closets, the last design we came up with (note that you can click on the 3D views to see 3D versions of the closet designs). The final proposed price was actually lower after rebates and some tweaks we could have done.

We tried some local companies first, wood, and then melamine, but they basically wanted $7500 to do all our closets. It just felt too much, so we started looking at other options (especially Jennifer).
Eventually, we found Budget Closets for a local option, downgraded our color from floor color to white, and Jennifer later found Coast Closets , which looked like the ideal and cheapest option: we eventually got a quote around $3200, but there were three catches:

1. the design had to be done via Email and or the phone since it was an order from the East Coast. We also had to take very exact measurements and be ok with having closets that would be slightly too small since they wouldn't be cut to exact fit on site. This would have been ok to save $1000, although designing and correcting on the phone was a bit frustrating and pretty time consuming.
   
2. the next issue was that we'd have to arrange for our own local install. In theory it's something we can install ourselves, but we just didn't want the burden or deal with potential problems if the install in the studs wasn't quite right, and later the cabinets fell because of too much weight in some of the anchor points. Problem was that experienced installers wanted to charge a ludicrous $1200-$1500 for a 1.5-2day install, which then made that option not attractive anymore. It would probably work better in places where contractors don't charge an arm and a leg.
   
3. but the last problem which ended up being the dealbreaker for us was that in order to offer better prices than just about anyone else, Coast Closets works directly with the mill and is constrained by what the mill can do, or extra charges they might add if we wanted some non standard cut (making the end price less attractive). Mark from Coast Closets really tried hard to help us, but our closets and needs were just a bit unusual and ended up requiring a bit too much custom work, making his solution not as much of a good match for us anymore.
   

After going back and forth on that solution and seeing how we could work with it, we ended up giving up and going with a small local installer/builder we found while looking for installers: Zen Space Solutions . It ended up costing $4500 at a deeply discounted price since he was trying to compete with the Coast Closets offer. The end result will be about $1000 more, but more custom and better finished. I guess this is what it takes...
At least, we didn't just throw money at the problem, and while it was painful and draining at time, at least we did proper research and diligence in finding the best result/price deal.
Otherwise, Budget Closets would have worked too, although they have more overhead and are more expensive, and for people who don't mind installing themselves, and Coast Closets is still the cheapest option by far if you are comfortable doing your own installs or have access to cheaper install labour than we did.