The author talks about his past experience, so did I. Back in 2014 the 1500 Euro Mac was beaten in image manipulating workloads (Adobe stuff) by a PC of the same price range.

Today, for a proper answer I'd had to check specific benchmarks and compare prices. If noise is no problem (e.g. separate tech room backstage, where the power amps live) used server hardware could be a reliable and performant option on the cheap.