Rough estimate......I know you asked for Audi owners, but I drive a VW and some of my parts are the same and say "Audi" on them
For VW, you have to take it in every 10,000 miles for a "check-up" to keep ur warranty in tact. Expect to spend about $100-150 each time for that. But that does include oil changes(which on their own are $75 each time) amongst other things. And for VW, they will tell you to get the oil changed every 5K miles early on, but after awhile you can wait to do it every 10K miles. And also, I would probably put mid-grade or premium gas in there only. I can definitely tell the difference in how the cars runs between those two and 87 grade
I'm sure Audi can't be too far off from that for the BASIC stuff.