I made a transition from freshwater to marine tanks in 1984, tried all the salt mixes (there were only 3 back then) and Instant Ocean always gave the best results, it was also the highest priced salt mix back then. i swapped to Reef Crystals in the late 90s and other then a few occasions where i could get IO at a ridiculously low cost i've stuck with the RC to this day. there was a time when 200g boxes/buckets were cheaper 'by the gallon' but lately the 160g buckets are more cost effective then the boxes and you can't get the 200g buckets any longer as far as i know. i try to stock up when i catch a sale and i rarely ever pay over $35 for a 160g bucket.
the comment about BRS showing the cost comparison of salts was based on their price which has IO and RC at twice what you can get it from most retailers. cost per gallon of Reef Crystals is 20¢ per gallon (less when on sale), their next lowest was 49¢ per gallon.