I upgraded a 1990 Trek 7000 from 7 to 10 speed about 10 years ago, this is what it cost. You can subtract out the cost of the dynamo lighting but you are likely to need all the rest. These were all rock-bottom prices from 10 years ago and most were decent quality, Deore, or better like XT, and all MTB components. I'd expect it to be a lot more these days, but I haven't priced things out. No one thing costs a lot but it adds up.
Since it was all better quality it has held up very well. I've never had to even re-true the wheels that I built myself. I may have replaced the chain a few times now, and I've added bits like better grips to the bars, and I had to replace an original chainring. I commuted in NYC on it for about 6 years before I retired.