I don't see why people doing something as a vocation precludes them wanting a decent amount of pay for it.
The context of the 35% pay rise claim is that this represents a return, in real terms, to the junior doctors' salary as it was in 2008. I would guess that this represents a peak, because the various graphs I've seen (eg
https://www.bma.org.uk/media/5508/20220114-juniors-pay-campaign_facebook4.jpg ) seem to imply that average salaries have only fallen since -- apart from in the Covid pandemic. But that's when sympathy for medical staff was presumably at an all-time high, and still represents only a "pause" a minimal real-terms increase of 1% or so (see also
https://www.nuffieldtrust.org.uk/resource/chart-of-the-week-what-has-happened-to-nhs-staff-pay-since-2010 , which provides a more comprehensive breakdown of salary trajectories, albeit since 2010, but also compares to the private sector).
Perhaps wanting to return at a stroke to 2008 levels is unachievable, and I wouldn't be surprised in this context if the various unions were prepared to settle for, say, a return to 2012/13 levels, which would be about half their pay demands. Then again, I'm not in the JD union, so what do I know as to what they'll settle for?
But once again the narrative that's skipped past here is that public sector pay has been significantly squeezed in the last 15 years or so, to the extent that many such workers have endured significant real-terms pay cuts. It isn't "greedy" to ask for that to be reversed.