I call bullshit on this.

There are lots of reasons why US academics earn so much more than their european counterparts, but the income level of US tech employees is not high on the list, if it is on the list at all.

Also, Baumol's doesn't predict that wages in low productivity growth sectors will rise, it merely notes that the costs in such sectors do not fall, which means that whatever the sector produces (good, services, art etc) become relatively more expensive compared to other production. This is why it appears to cost so much to see the symphony orchestra, even in Cincinnati - it's not that the players all make a ton of money, it's that their productivity is flat, so the costs of the performance appear to rise relative to, say, toothpaste.