well I only wash it myself, I think I've been to drive thru car wash twice in two years. Since using No Rinse I haven't "washed" my car in months. Probably twice a month now. It takes no more than ten minutes with No Rinse and I'm getting qiucker at it. Probably takes longer to bring the bucket and towels to the drive way then actually cleaning the car. And since I only use quick sprays now and have dumped paste waxes that detailing part only takes another 15 minutes.
25 minutes twice a month is pretty good me thinks.
I don't detail between washes mostly to avoid swirling and because FK do such a good job at neutralizing dust. If it rains its actually a good thing because all that dust runs off the paint on its own. And of course the car is silver!!! very low maintenace
When I had my black car that was a real PITA at least 5 washes a month and several hours of monthly torture.
As far as budget I buy by the gallon whenver possible. A gallon of FK 146 quick detailer is $25 each. Spray Wax by Duragloss is also $25. This will easily last six months. Polishes and sealants and Leather cleaner/conditioners are only used 4 times a year and one $15 bottle will last at least two years. The products that go quicker are tire dressing, Plexus, and 1Z interior sprays like cockpit premium and Vinyl and Rubber care Probably $50 every six months. Again I spend no more than 10 minutes on the interior by doing it often like twice a week. Red is a great color to keep clean you never really see dirt and always a nice shine. My friend who used to detail for a living is buying his VW convertible in silver red out of spite.
The expensive part really is buying all this detailing stuff for the first time: PC buffer & pads, half dozen different brushes, Towels, etc. but then your good for years.
I'll end up spending $500 for everything but after selling my last car for twice the private party blue book value I definintely see the advantage of catering to a future enthusiast owner of my BoxsterS. Not unlike selling a well maintained house.