I just got 100 lbs of ZapIt73 from Warehouse Pool Supply for $160. 73% cal-hypo.
This is fine for general chlorine needs as long as you are just a bit low on CH, if you are really low it may not make sense to take such a long time to get back to the right range.
In my pool, 1 cup of 73% cal-hypo gives me 2 ppm FC and about 1.something CH. So that is a daily dose of chlorine, but it will take a long time to add 60 pts to CH. For that reason I find this fine to get from the bottom of the suggested range to the middle or top of the range, but it one is far below the minimum, probably better to bite the bullet and buy some calcium increaser.
I recently found that I was low on CH. I had been having issues testing, globules formed in the test, and I was not certain of the readings. Let it go for too long in these heavy rains. Pool store read 200ppm hardness, I read 170 ppm CH, I think mine is correct. I bought some calcium increaser to get to 200 ppm, about 20 lbs, and will use the cal-hypo to get up higher in the recommended range.