$25/hour flat rate? Why? That's not even half the market rate for an average developer.
I somewhat agree on having "auditions" or at least a quick try before you buy, if you will, but at least pay a decent wage.
What would work best imo is to technically vet the candidate early on and over the phone. Perhaps a 30 minute pair programming session done in stypi where you're both working on some code. After that do a group skype chat session with some other teammates and the candidate to see how well a group conversation goes. Nothing extreme just a 30 minute to an hour pow wow about the job, the company, etc.
If the candidate is still in the running then bring them into the office, if you actually have a physical office, and give them a couple hundred dollars to work on some code for 3-4 hours. See how they fit with the team and how well they perform in person. You'd be surprised at how quickly you can get a feel for someone. It doesn't need to take weeks. If you're remote you can do the same thing, in fact it'd be much cheaper without having to cover the candidates travel expenses.
So how many people would even make it past the first round? 10%? lower? After that you've got a nice number of qualified candidates and plenty of opportunities to weed them out before anyone wastes their time.
In this case, that should be part of the hiring risk that the company takes on, else you're punishing the good developers, who presumably you want to join your company, for something they have very little control over.
Tell your barber that you're going to pay him 1/2 from now on because half the other barbers in the city are worthless...
You've got bigger problems, tho. A headhunnter fee is 30K.[1] Take 30K and divide it by 50, and you have over 600 hours to play with. Lets save ~85% and take 100 hours as your budget @ 2x the cost. That would cover how many work-sample tests? (take your pick) 20 peple x5hrs or 24x4hrs which should be a good funnel. What's wrong with this approach?
[1] Assume a 100k position., which is also $50/hr on 2000 hrs/year.
I think OP was asking from the seller's (interviewee's) perspective. $25 doesn't buy a lot of time from a software engineer. And from the hiring side it seems like you could easily justify a higher amount based on time saved on interviews.
I somewhat agree on having "auditions" or at least a quick try before you buy, if you will, but at least pay a decent wage.
What would work best imo is to technically vet the candidate early on and over the phone. Perhaps a 30 minute pair programming session done in stypi where you're both working on some code. After that do a group skype chat session with some other teammates and the candidate to see how well a group conversation goes. Nothing extreme just a 30 minute to an hour pow wow about the job, the company, etc.
If the candidate is still in the running then bring them into the office, if you actually have a physical office, and give them a couple hundred dollars to work on some code for 3-4 hours. See how they fit with the team and how well they perform in person. You'd be surprised at how quickly you can get a feel for someone. It doesn't need to take weeks. If you're remote you can do the same thing, in fact it'd be much cheaper without having to cover the candidates travel expenses.
So how many people would even make it past the first round? 10%? lower? After that you've got a nice number of qualified candidates and plenty of opportunities to weed them out before anyone wastes their time.