I totally where you are coming from and we have the exact same discussion many times here but we have to protect ourselves from bonus abusers and a min initial deposit of $50 is the least we could do.
In the long run if you send quality player and they want to take advantage of a great sign up offer of 200% the $50 is really not all that much.
The other option is to go on a evenue share deal
Hope this clarifies the issue.