My opinion is that freelancer.com is not a good place to find quality SEO services. The problem is that developers are competing against low cost workers in places like India which is forcing everyone to drive their prices down and the end result is that the quality of work delivered suffers too. Everyone is trying to turn a quick profit by doing as little as possible.
I would agree with the above comments, this is not a quality SEO package as it is mostly based on strategies that used to work but have drastically been devalued by search engines recently (do some research on Google Penguin for instance) and is more likely to get your website penalised in future. I have sadly had the experience of trying to recover from these penalties and trust me when I say it's not something you want to go through.
Why do these guys have great reviews? it could be a number of reasons. As mentioned already the reviews are not all genuine. Another major reason is that the majority of the users buying SEO services do not understand that what they bought was low quality! They see the work has been delivered quickly and are happy and offer a good review, they may even have an initial improvement in rankings. What the review may not tell you is that they picked up a penalty months down the line when the work is paid for and Google has caught on (it's happened to me).
What would I recommend The sad truth is that today when buying SEO services you need to become fairly SEO savvy yourself because there are still far too many black hat SEO's trying to make quick money who will offer you these services. Spend time on this forum, read the articles and become familiar with which tactics are future proof and which tactics are now considered black hat and dangerous. This way to can judge for yourself if a proposal is offering you value. Try find a local agency or freelancer who you can talk to easily or meet in person rather than someone who will do quick work and then you will never be able to contact again. Link building is an expensive game now because there is no quick, safe and easy way to get results any more! If you have a low budget then go after one quality link pre month rather than 100's of rubbish links. You need to find the right people who have the skills to get your content in front of the right people in your industry and build natural links.
It's probably not what you wanted to hear but hope that helps in some way.