You're missing the part where some people, that actually would need this support, literally wouldn't be able to find that money because of the difference in purchasing power of the local currency.
Phillipines is a good example; Average yearly salary is somewhere around 12k USD, Median is 8k USD.
That means if someone is doing a tech startup there, 300$ is somewhere between a quarter and a half of some employee's pay for a -month-. And given the potential for tight margin/cash flow of startups even in the US... it would still price a lot of smaller players out of the market.
You need an adjustable amount that is based on the annual income/revenue of the person/entity making the request.
Make it high enough to be non-trivial, but not so high that it blocks all effective usage of the safety valve.
Now, if you can solve that problem, I've got some bridges for you in Arizona.
This is a good way to filter the full level of importance. Most places that need a problem solved, now, dammit will be willing to pay.
And, if you want to be nice, you can refund it. Or, if the person was a jerk, you can keep it.
If it is refundable, make it $300. That is high enough that only people and businesses with a showstopper situation will use it.