A donation is a thank-you, a recognition that although the internet is a free distribution method what was distributed "had value to me and I appreciate the effort that went into creating it."
"Asking for donations is still quite rare."
At the risk of stating the obvious a web site has two costs, the cost to create and maintain it and the cost to host it.
We all know that good, useful web sites take a lot of time and effort to create and we are accustomed to them being free.
So asking for donations is still quite rare on the internet, but it is becoming more common although it is still a tricky thing to do as it can get people's back up.
I try to explain the subject in this way; Cup of take-away coffee, £3, that's fine, magazine £5 an issue, that's fine, I've spent a hour on that web site £3, that's fine,
"Web sites are easy to create, I did one for my local club."
Simple web sites are indeed easy to create, however this calculator isn't really a web site, it is a serious bit of programming that just happens to have a browser as the front end.
it's not just the time spent coding the simulation or the web site to display it, it's the time spent on research, how many times have you looked at a web site and thought that's just cut and paste from another site?
To put this into context I have roughly 160 hours invested into this project so far.
"I thought that hosting was almost free?"
If you have a simple site then it is possible to get hosting that is almost free.
For the hosting company to be able to offer such a low price they tend to allocate a lot of web sites to a smallish pool of resources and if your site takes up too many of those resources you are asked to move on to a more expensive plan.
Once you need to move on the price start to increase rapidly and it is very easy to be paying £600-£1,500 per year to host what seems like a simple site.
It is a combination of how complex the site is, what it does times the number of users, especially if you have a "Save My Simulation" type button (database demanding) or complex calculations (CPU demanding).
"Can't you just stick some adverts up?"
The trouble with advertising is that it gets in the way of the page layout, if you don't stick your adverts in the most annoying places on the page they won't be clicked on.
I am experimenting with well placed and carefully considered adverts along with links to other sites of mine, but the typical industry norms don't seem promising. For example one mail order bike dealer was offering a £10 commission on a £1,000 bike but only if the customer ordered within 30 days of clicking on the link and there is a delay period typically between 30 and 140 days before the commission is paid.
Added to which adverts can easily create the impression that the site was created to sell advertising rather than do whatever the site was set-up to do. After all many sites do exist solely to sell advertising.