In my opinion to buy hyaluronic acid gel is a nonsense, it is way better to homemade your own.
The hyaluronic acid in the link you provided is largely over expensive and misleading, in facts it is impossible to have a 100% hyaluronic acid gel (by the way since it comes with a pipette cap it is not even a gel but a serum or a very low percentage hyaluronic acid).
First, what is called hyaluronic acid is actually not an acid but a salt (sodium hyaluronate would be more appropriate of a term) and as far as my knowledge goes proper hyaluronic acid is not to be found on the market and not desirable too, anyway it comes in a powder form which is never 100% pure as almost all compounds, a 98-99% is already more than satisfying.
Second, in order to get a gel a maximum 2% of hyaluronic acid powder can be mixed with water, more than that leads to a solid mass impossible to handle and undesirable for other reasons too.
Third, unless very small amounts are made (no more than 30 days supply) and kept in the fridge a preservative is needed in order to avoid bacteria and molds formations in the gel since the environment is quite inviting for those unwanted organisms to develop.
Claiming 100% hyaluronic acid is therefore quite inappropriate.
In order to make your own put 30g of distilled water in a glass container provided with a lid (I use those fake caviar small jars), add 1 drop of SSKI as a preservative (you can make your SSKI adding 14g of potassium iodide in 10g of distilled water in a glass container provided with a pipette cap), add 4% niacinamide powder (1,2g), stir till dissolved, now add between 1% and 2% hyaluronic acid powder (0.5g at 1.5%).
The hyaluronic acid powder will not dissolve and float on the surface, stir and it will clump horribly, don't worry, stir a bit, place in the fridge and wait for 12 hours, stir again and you are done, if it is still a bit clumpy leave it in the fridge a bit longer, after 24 hours it will be certainly ready for use: a beautiful crystal clear gel.
Keep it in the fridge even if with the add of SSKI it would be safe to keep it at room temperature, 30g of gel would last approximately 30 days of daily use on the whole face.
Since the cost of the SSKI and distilled water are negligible you can consider the cost of 30g (slightly more than 1 OZ) as the cost of 0.5g of hyaluronic acid powder which is about 1$ (http://purebulk.com/...ic-acid-powder/).
Now you have got the best "pure" hyaluronic acid gel you can possibly get at about 1$/month which can be used by itself or as a base for any water soluble compound you wish.