I do the latter. I also know the chemist who formulates the BBW, he also makes cleaning chemicals for several other small breweries locally (including where I work) he is also a home brewer.
Fair to say I believe that good cleaning products and using them properly are very important and put value on a product doing the job I want without any unexpected side issues.
Often using the right chemical the wrong way can be just as bad as not using the right product, (i.e. some acids used well will remove beer stone, same chemicals will dissolve a tank at the wrong concentration) another example is the often cited notion that Citric Acid will passivate Stainless Steel, it will under certain conditions (usually adjusted temperature and time with additions of a buffer and for some grades of SS K-Dichromate and or copper salts...).
Point being that just sprinkling citric acid on a weld and saying abracadabra probably wont get a passivated weld, using the right products (some with citric) the right way will.
Cleaning and sanitizing is a vital part of the brewing process, as pointed out above the right chemicals are often less expensive than supermarket rando crud. If you think about it using a quality product from a good supplier is only going to cost you (say Perk @ $6/kg, 50 g/brew) 30 cents a brew (maybe $1 for BBW or the like).
Often complete rubbish and a bit of boiling water will do a good enough job most of the time - 1 infection or contaminated brew in a decade and you will loose more than you save trying to find a cheaper answer.
Frankly strikes me as a pretty pointless exercise, use the best product, use it properly make good beer!
Mark
PS
Sp0rk, yes I know All Pro, good for glasses and kitchen ware done a fair amount of shopping there, some good floor cleaners, glass and dish washing detergents to, not so much for brewery cleaning.
M