Probably my favorite thing about fertilization is that there are numerous ways to skin this cat and still deliver great results. Since there are so many different fertilizer possibilities, every LCO in a particular market can have something different and still deliver a green and growing lawn.
That said, I have two caveats about selling a micronutrient program:
1) If you're saying that you're doing something different than your competitors, you need to be sure. In all the places I've operated over the years, they've all required an invoice or some other statement listing what I applied. We all know that neighbors talk and if one of your customers finds out that another LCO in your market is applying the same thing that you are (even for just one round), your credibility will be toast and you could even face a lawsuit from your competitors.
2) Customers may see the additional charge as "nickel-and-diming." Also, if they don't see a huge improvement, they will think you've ripped them off. Nothing worse that a customer paying for your basic service, then paying extra for micronutrients, and seeing their lawn no greener than the neighbor's lawn who doesn't have a service or fertilize at all. I tell my customers that I will supply their lawn with whatever nutrients it needs to perform its best. Spreading the cost of any extra nutrients over the whole customer base amounts to a price increase less than 5 cents and it shows my customers that I care about their lawns, not about ripping them off for more money.
Just a quick note about pH changes in soils. It usually takes LESS sulfur (elemental) on a per acre basis to decrease pH than it takes lime (CaCo3) to increase pH. It takes about 1 ton of elemental S/A to drop pH from 8.5 to 6.5 (2 whole points), but it takes almost 2 tons of finely ground limestone/A to increase pH 1 point from 4.5 to 5.5. There's no reason to make a big deal about using S to drop soil pH. Just think of it as the liming for the high pH parts of the country.