Sticking my neck out to be shot down, a flouro-carbon is a flouro-carbon is a flouro-carbon. My impression of the products is that the higher quality products don't necessarily give better stain/soil resistance, but are more durable so perform longer.
Many years ago, when Derek first started shaving, I also attended the above mentioned Prochem Training Course. Uncle Ron (Tilley) went into this debate quite convincingly, preaching that the Prochem products performed much longer than most of the competition and was amongst the best on the market. I admit to agreeing with this viewpoint. He went on to tell us that some other brands they had tested themselves had lost their resistance properties after the first vacuuming.
I now use Chemspec's Enviroshield which is , I gather, identical to Stainshield Profesional, which has a higher solids content than the ordinary Stainshield (no license required for this product). I believe that this makes the higher grade products more durable rather than better performing. Some figures I remember from the past, which I trust are accurate, was that correct cleaning will remove about 3% of a good quality protector. Another 2 or 3 % will have been removed with wear and tear over about 2 years. You need a 10% reduction before topping up the treatment, which is usually at the 2nd clean, and may be for traffic lanes only. My own experiences support this statement. This applies to residential carpets only, and not commercial, which may require treating at every clean.
As far as pricing is concerned, I would always advocate working to a standard, not a price. You can then set a price accordingly. To do this, a premium service requires premium products. So never undersell your services.
I have used primarily premium labeled products in my business, and although there will be lower priced good to serviceable quality products available, I do not have the time or means to go around applying, testing and monitoring all the products available. By keeping to well known, trusted brands, I have faith in the products and back up provided. The difference in material cost per sq.M isn't that great.
Protector is a product for which I would not give the "hard sell". Although the products can perform as the manufacturer intended, the customer quite often has a vision that a spillage will "hovver" just above the carpet and not penetrate into it's structure. Therefor, a protected carpet should never need cleaning or require mopping up after a spillage
Safe and happy cleaning:)
Ken