The Stack Exchange reputation (and voting) system is pretty complex, and your suggestion is a very small and simple idea.
How would this idea fit in to the rest of the Stack Exchange rep/voting systems?
Also, why would this be better?
why doesn't Stack Overflow use this system?
On Stack Exchange sites we currently get to ask questions for absolutely free.
And we get 2 rep for accepting an answer.
If we ask a good well written question, we likely gain even more rep.
If we are lazy, and ask a duplicate, or a poor or off-topic question, we likely don't gain rep, and often lose some from downvotes.
This encourages better quality content.
Stack Exchange's model sounds better to me.
What if you don't have 5 (or whatever) rep to be able to ask? It could have been a great question, with great answers, now lost forever and no-one gets to read that great or even "just" helpful answer.
Having to "pay to ask" potentially hinders our being able to create a large collection of information, as many users won't have the rep to ask.
What benefits are there from needing to "pay to ask"?
It seems like a pointless exercise to me. Paying to ask a question in no way guarantees a well written or quality question, or even a good question, whereas on Stack Exchange sites we earn rep by doing good things - this promotes and encourages good content and quality posts.
Paying does not do this.
It also has the potential to push users to carry out rep earning tasks so they can ask.
Forcing people to do such things means their intentions are (possibly/sometimes) not in the interest of the site.
They just want the rep, so do a poor review, or post a poor answer, etc, just to get some rep.
This can be seen by comparing how much quality content is on Stack Exchange sites, to that of Yahoo Answers.
It would be much more convenient
Here you ask for free, and get 2 rep for accepting an answer.
Yahoo Answers you pay 5 rep up front, and get 3 back.
The net outcome is you lose rep for asking. I can't see why this could be considered a good model.
Some people do not want to or have an answer, and so with the Stack Exchange method people can ask if they want, answer if they want, etc. And they simply earn rep based on activities they are comfortable with (and what others believe the quality of their post is of course).
This is more likely to encourage good content, as users are not forced out of the professional or comfort zones.
and those with very little rep wouldn't be able to ask very many
I really have no idea whatsoever why this would be a good idea.
Stack Exchange allowing everyone to post for free (with some posting limits of course) is much better, especially as we have a great community moderating system to be able to resolve any problems and poor posts.
And the automated site scripts can slow people down if they're posting too many bad questions/answers/etc.
Again, the Stack Exchange voting and thus rep systems are very complex, with many functions and parameters, of which have the potential to affect each anther.
So you cannot just "shove in" a new idea like yours.
Also, I just do not see why the Yahoo Answers model is any better at all, in fact I think it's bad for reasons as above.