The piano in ensemble. The piano in real life.
Firstly a couple of things:1. According to what research? I know it's a meme but I'm guessing there's some truth to this?2. I did a lot of collaborative/accompanist work as a pianist (17 in one year) and can tell you that while the pay was generous, it would never amount to what a solo pianist (of high standard playing in gigs and concerts) earns in a year. It's really case of quantity over quality: if you were to give me fewer engagements but with the potential to earn anything near the likes of Lang Lang, I would take that over lots of gigs.
Great comment, Charles. Yes, top-flight solo pianists do make a lot of money. However, there are only a handful of them that can be supported by the concert and recording establishment and their audiences. The vast majority of solo pianists make much more modest fees playing at smaller venues. As a collaborative pianist, I've played played many engagements where I actually made more than the soloist (who had a huge amount of expenses to pay out of their concert fee). Collaborative pianists' expenses are usually covered on tour. They don't need to pay for recording and promotion expenses, and rarely do they need to pay an agent. So while collaborative pianists make on the whole a more modest amount than top-flight soloists, they have only a small fraction of the expenses, as well as more gigs. I don't know of any research regarding the frequency of engagements of collaborative pianists versus solo pianists. The meme was based on anecdote.