Otherwise, it's a completely different story.
As a developer I've used Toptal in the past and honestly, they're doing a great job. I'm based in central europe where average salary can be as low as $22,000/y. Toptal allows you to 3x-5x that easily by working 40h/week, 100% remote.
It's literally transformed hundreds of lives within my city.
There are tons of long term projects (6-12+ months), and I've never had problems finding a new project (front-end, js). Once I start looking, I expect to be working the next week.
For some, it's a great long term solution. For others who are more ambitious, it's a great stepping stone into the $70-100+/h market.
They do take a pretty big cut, but the developer is still left with tons of cash.
I dropped it after a while, because I started receiving fat offers directly from other clients, but I'd still recommend it to anyone who doesn't have a well developed client network.
Why would you keep your local $30k/y job when you can work full-time on Toptal for $80k/y?
Toptal covers hourly (min 10h/week), part-time (20h/week), and full-time (40h/week) engagements. Some months I've worked 60h/week (on my own accord).
I'm not saying any of this is fact. I'm asking for clarification since you have first hand experience.