To cut the prices a little for the guest posts use this method:
1. Subscribe to every newsletter, related to your niche, from the sites you want guest posts. Use the mail:
[email protected] or something like that, you get the point - make it look serious.
2. Respond to every newsletter you get with something like "Great post, as always, I love this newsletter. Keep the good work!!! I have shared it on twitter and facebook, *link*" (You can colour it a little)
3. After responding for a month to every newsletter it's time to try and get your link up there. "Hello, again very useful post! By the way, I have just finished an article, related to this post, mind sharing it on the website - I am pretty sure it will benefit your readers even more."
Note: Since few subscribers are responding to these newsletters your emails won't be unnoticed - you will get their attention for sure. The more chatty you get with them the better.