Websites like Upwork have a monopoly of the market and they know it, this is why they can exploit their workers for 20% of their pay and most just keep silent about the abuse because they want to keep the chance of making money on the platform but the truth is that is quite difficult, not only clients ask you to do something for cheap for the most part they do not even know what they want so it is almost impossible to make an effective proposal to try to gain the job.
You wont really have any choice but to deal with it and you're right that people would just deal with those deductions rather than losing up their job or spot, knowing that getting some freelance jobs online is really difficult due to competition thats why they do just swallow their pride and just accept into their pay even though they do know that deductions are too much.Do they had that options left? none. So they'll stay on what it is.
Actually this doesnt only killed design and dev business but on other skill-set as well.Is there any other way? theres none unless if there are freelancing platform would offer much more lower but as said that
majority of them are on monopoly side of things then you can expect these numbers.
The only real option for those in those professions is to try Upwork for a time and then gain a reputation and clients that way and then try to get them out of the platform, this is without a doubt hard but if you can make a very good job many clients will follow you as there are many businesses that do not really care that much about the cost of the service as much as they care about the quality and the time it takes them to receive the service they want.