Most inexpensive sources of DHA

Been doing a lot of reading today on DHA and the impact it has on so many things.  Strongly (strongly strongly strongly) recommend you do some research yourself on the impact that DHA (or lack thereof as is so often the case with SAD) can have on the human body.  Decided to calculate the cost of various forms of DHA tonight.  Pretty interesting.  Here's what I found:

$13.59/43.2 G of DHA Nature Made Fish OIl (Costco.com) = $0.31/G

$11.25/12 G of DHA NOW Omega Supreme (NutritionGeeks.com) = $0.94/G

$40/40 G of DHA Vital Choice Sockeye Salmon Oil = $1.00/G

$20/12 G of DHA Omega Zen-3 (Sunfood.com) = $1.67/G

$25.19/6 G of DHA Neuromins (SmartBomb.com) = $4.20/G

$89/9.63 G of DHA Vital Choice Wild Alaskan Salmon = $9.24/G

These were calculated by taking the recommended dosages or serving sizes and multiplied by the amount of DHA per dose/serving.  On a per cost/gram basis Fish Oil from Costco is less than a third as expensive as the next leading contender.  However, I'm a little dubious as to how that's sourced and if you're looking for a vegan form of DHA it looks like NOW's Omega Supreme oil might be the way to go.  I've heard a lot about Omega Zen-3 but compared to Omega Supreme it's almost twice the cost per gram.  Neuromins is over four times the cost so unless I'm missing something here I'm not sure why you'd want to go that way.

And the worst choice (at least on a cost/gram basis)?  Salmon itself.  Almost 30 times more expensive than Costco fish oil and about 10 times more expensive than NOW Omega Supreme.  Seems like a pretty inefficient way to get your DHA...

Now I'm not sure all of the other things that go into this analysis and I'd love to hear thoughts on this form of analysis.  At the end of the day it seems like we all should get more DHA in our diet and given that this can get pretty expensive I hope this data helps some people make better choices!