When it comes to tunnel washes, "price" is usually calculated on a blended cost/car average. This can vary widely depending on the tunnel setup, chemical delivery systems, wash package offerings and operator preferences. If you're shopping chemicals, I would focus more on the "who." A good chemical rep/company will work with you to get the cleanest, shiniest, driest car you can get with in your budget and quite frankly, show you how you can make more money with your offerings. In addition, they will provide the technical support and hands on support that you need to put out the best product to your customer.
I have tried perhaps 100 different products for most applications. 95% Did the job and gave the needed show. So, then it comes down to cost per car. When I try something new I simply swap it out for the current product. If it does the job and has good show I see if I can dilute further with the same results than compare cost to what I use. Or if it needs the same dilution - same comparison. Here is the current mix. Low PH Triple foam soap, Triple Foam Polish and Sealer wax from Kleen Rite.. From Simonize Foam 5 for high foaming bubble arch, Wheel Cleaner, and drying agent. Rain X for the high end treatment. (I think the name recognition is worth the cost) Viper Shine for Tire Shine. I load up from KR when they have the buy 3 get one free sale and always get the free shipping and top off the pallet with other supplies and vending items.