I usually plan my purchases. For one, I need to budget them. So I do my homework, research prices, and plan where I am going to buy things. I make up a lot of excel spreadsheets. I need, this, this, this and this. And I may get those things at 4 different places. Most of the places I buy stuff can be found on my way home from work. If not, I will wait till I am going that direction for something else and buy it then. So an extra day or two doesn't make much difference.
If I need something tonight, right now to fix my car so it runs for work tomorrow, $5 doesn't matter to me. But then, I don't even consider internet in those cases anyhow. So no, time frame doesn't matter much to me.
As for doing the research. I usually get to work 20-30 minutes early which I use to do things like this. Also, I have to take an hour lunch. I spend 15 minutes eating, and the rest researching stuff and on forums. I also get on a couple times a day depending on my work load. So the time factor researching these items is null.
And while I agree that price is not my only factor on buying things, it is very dependent. There are places I just won't buy from and won't even consider. But there are very few of them.
I agree with you as well that vendors will charge what they want. Doesn't stop me from voicing my opinion on it though. But really, I do understand this. And there are many products that I feel are over priced because I know their true value of how much things cost to make them. I don't mind paying someone a profit. But I don't like paying for overpriced items either.
In regards to your water to gas converter. If you were the first one to come up with this, then yes, you can charge that much. And more times than not, it is because of the R&D involved. But when other people start producing similar items and selling at less price, you will eventually lower your price till you are near the $25 price window that it costs to make the part. Economics will show that if you are making a huge profit, there are a lot of people that are going to try and get onboard as well and make the same profits, but undercutting the competition a little each time. Thus driving prices down. Eventually it will all equal out.
On the other hand. If someone already makes a water to gas converter, and your works only slightly better, the price needs to be comparable to the benefits. You can't sell yours for $250 for the upgraded model, versus $25 for the standard competitors model.
And this entire discussion started about the SS brake lines. I started it by saying that I felt that when a vendor can discount a product $32 on a $100 part, then this product is overpriced (in my opinion). The way I see it, while some places will discount items to where they are making little to zero profit, most smaller vendors will not because they cannot afford it. ZZP may be doing this in this case, I don't know. But usually such offers are one time deals, like the woot deals. But being that these brake lines were offered up again at such a discount would lead me to believe that ZZP has inflated the price to almost, but not quite match that of goodyear lines. And they haven't been selling as well as they hoped, so they are trying to get more sales and get these moving. Might not be the case, but it is how I perceive things, and my opinions.
I personally think $100 brake lines are overpriced, since I know how little it takes to make them. So I haven't bought any. These prices ZZP is offering now are comparable and much more in line in my opinion and I will probably purchase a set in the near future.