0.05 BTC for 1 month seems to be a very low amount for your actual (Legendary) rank.
If you make arround 50 posts per month (as you stated) you can easily earn 100$ monthly if you join a signature campaign.
That's the reason why it's an auction with the
starting bid of 0.05 BTC. If I joined a sig campaign I not only would be at the mercy of whatever restrictions / rules / exclusions / etc. the manager put forward but would also have to remove both the advertisement notice and any of my personal links.