You can't sign up to be in the top spot for $50 a year.
Search engines generally have two sets of results at a minimum. There are the paid results and the raw search results.
With Google the paid results are on the right hand side of the screen and in up to two places in the main body at the top of the screen. The raw search results are in the main body. These paid results are on a per click basis. Google gives them priority placement based on an algorithm that looks at cost per click, budget, and frequency of clicks. You can really only get the best spots by paying a lot of money per click.
Yahoo does the same thing. They also put many paid search results in the main body of the SERPs though. Bidding on these is done through Overture, a company that Yahoo bought. They are placed pretty much on a highest bid, highest placement system. They will cancel your ads if they do not get a high enough click through though.
You can also pay to be listed in the Yahoo directory. It's a few hundred a year and doesn't guarantee you anything in the SERPs (search engine results pages).
There are people who are paid good salaries to do nothing but try to get good search engine placement by companies that make a lot of money off ot it. It's not a simple matter to get good placement on competitive terms.
Google looks at keywords but also PR
is a value derived from the number of sites that link to you and the PR
value that they hold. So incoming links help you get better results.
We do have a search engine friendly archive here to help. You can find it by clicking on archive in the lower right hand side of the screen.
I could go on and on about this topic. It's not a simple matter of paying $50 a year and getting top placement for all the keywords you are interested in.
If that were true I'd pay the $50 to get top placement for asbestos cancer. Lawyers pay up to $100 a click for associated terms. Using Adsense you'd make a lot of money buying top placement for a year at $50 and earning your share of the clicks for the next year.