I think that's probably about the best price you're going to find. I tried googling for spirulina and almost fell out of my chair over the prices!
I'd save your money and not buy it all. The B12 analogues in it can mess with your B12 absorption and there's nothing particularly brilliant in it you can't get in abundant quantities from any number of fresh, raw foods.
What does it taste like? Is it fishy or kinda mouldy?
People always say, "ahhhh spirulina tastes like nori". Maybe my taste buds are whack, but I don't think it tastes anything like nori. I love nori and could eat it by itself all day long. Spirulina? Not so much. I had one of those "complete" juices one time and spirulina was the main ingredient. To me it tasted like what it would taste like to lick sludge off the bottom of a river. It kind of reminded me of times when I was a kid and would play in stagnant ponds like a moron and some of the nasty water would get in my mouth.
To me, spirulina is one of those fad "miracle" foods that they charge a ridiculous amount of money for and I could get the same nutrients from much better tasting (and less costly) fresh foods. You also have to be really careful about the source of the spirulina. Contamination is a huge concern with spirulina, so you have to buy from companies where it is pretty much cultivated in a special environment (such as a special lab type "farm" where it is completely sanitary to prevent fungal and bacterial contamination).
Also bear in mind that a lot of the health benefits that have supposedly been discovered were tested on animals, such as how it helps people undergoing chemotherapy or have heart disease and also as a weight loss supplement.
OMG it's gross! i used to put it in smoothies but you had to use such a tiny amount to not spoil the flavour (and it turns it green and it looks horrible) so now i buy it in tablet form instead...that and chrollera (cant' spell it) another algae.
I bought a relatively cheap dried 'seaweed salad' mix ages ago in one of the health food shops in Dublin that I discovered has spirulina in it. I'd say it was about €5, maybe less. Its just one of those things I keep in my press and add to miso soup or rice noodles.