If you take the price per bottle (of the topcoat, basecoat and colour coats) divided by the amount of applications possible, it gives you a basic cost per service. Assuming you’re using the same prep and finishing products for all brands, the cost will be the same. Your heating, rent, electricity, time etc. will be exactly the same whichever brand you’re using.
So if a 15ml bottle of brand x costs £25 (say there is 40 applications per bottle x 1 basecoat, 2 colour coats and 1 topcoat)= £2.48 per application. Say brand y cost only £10 for a 15ml bottle = £1 per application. All other costs are the same, so if you’re going to charge less it should only be £1.48!!!! Where I’ve seen techs discounting for cheaper products it’s usually £5 less, meaning they are losing £3.52 per service or £28 for an 8 hour day or £140 per week straight off their profit margin.
Techs who charge less for cheaper products are not really doing the maths, and are effectively making far less profit on cheaper products.