It is much more cost effective to pay someone $100 to write and distribute a nice press release about your site. If you pay $200 for 4 submissions and that end up being just 4 average backlinks to your site. Google may or may not send you more visitors for that.
But...
If you pay someone only $100 or so to do a press release, you will get many instant visitors and the press release will create temp backlinks which will also raise your
PR until the next update.
Enjoy!