Agree 110%. People just don't ask. But people starting out assume they will ask, so they get nervous and maybe even bring it up themselves.

Also I used to charge super cheap, because I figured it was good for me to learn and good for them because they pay less (highly not recommended).

Charge a decent amount upfront, it means you can spend more hours working for them, they will value your work more, respect you more and a whole list of other things. Also if your in competition with other people bidding too low will only land you the worst clients. The best clients pay more and because they are successful will respect your time.

In a sense you have built a portfolio of connections. You spent 4 years developing relationships, building your communication, and getting to know people in the industry. Your experience shows there are many ways to approach this but I would say experience is definitely a prerequisite for any freelancer. Weather you spend time building a portfolio or an amazing network of connections in this industry, you gotta put in the time.

I'm also starting as a freelance after some years of web experience in startups and agencies but I have trouble finding these hundreds of people. Could you elaborate on this?

It really depends on where you live. If you live in an urban area with a decent population there will be people you can meet face to face.

If you live in a rural area it's going to be a lot harder to meet people in person. In that case focus on finding online leads or consider moving.

I second that. Meetups begat meetups and leads begat leads, you can contribute things to the conversation and show your experise (your oral portfolio). That is how I look for developers. Things will fall into place. You just have to get out there.

Last year I started thinking I might one day go freelancing, so started attending relevant meetups and trying to figure out who to connect with locally. It was partly that which lead me to build the http://jobstractor.com (shameless plug) to try and find who was hiring near me so I could connect with them on twitter and start getting myself known. I've not made the leap to freelancing as of yet but networking has I think got me in a far better position should I want to in future.

To the OP, I did find that a lot of people in the local freelancing community were strongly connected with each other. A little bit of networking could go a long way and in my experience there has always been people looking for good developers.