My $0.02 about feed through supplements is that they rarely actually work.
My vet has said that he feels bad about selling feed through supplements in his clinic because scientifically they don't work and people shell out a lot of money for them. Glucosamine and HA in particular are actually too large on a molecular scale to be absorbed by the horse's digestive system, and just end up in their poop. MSM and natural anti-inflammatories (like Yucca and Devil's Claw - which will test if you are showing) do work to a degree.
And another point I would like to make is that most of the oral glucosamine comes from shark fins, which is the leading cause of the world-wide decline of sharks.
What I would recommend is talking to your vet about what kind of protocol he would like to have the horse on. A lot of vets will recommend for "budget" regimes once monthly IV Legend (about $70 plus the farm call), once monthly IM Adequan (about $100 plus the farm call) or once monthly glucosamine (which I don't use so I can't say a price, but less than the Legend for sure) depending on the results of a simple palpation of the joints and a flexion test.
If you are really into "bang for your buck" it might also be worth it to think about doing a twice yearly Adequan regime of 7 shots, one every 4 days with no monthly maintenance between. Do one before show season for sure, and that might even hold you for the whole year if you give your horse winters off.
If you add up the price of these once monthly, or once/twice yearly options you are looking at between $1000-1500 per year, which is about the same cost as any "good" feed through supplements ($100/one month supply), and you will see far better results.
They say money doesn't buy happiness -- well happiness doesn't buy horses!