Back on Elance popular projects that received a ton of proposals usually numbered within the 30-40 range (within the social media marketing and copywriting categories). I just saw a job that had more than 100 proposals. I have to say, if I were a hiring client, I would be totally overwhelmed by that. Ummm that's all, I'm just really thinking out loud because that sounds like a ton of proposals. And they were probably almost all bad.
Indeed, It must be really hard for a serious client to separate the wheat from the chaff on Upwork. I'm a strong believer of the fact that Upwork's business model is centered on the pursuit of what they call the long tail, which is the huge amount of low paying jobs, which makes this platform a valuable resource for low price outsourcing.
The success lies in the volume, lower the prices, greater the number of interested clients and greater the amount of contracts.