in his bio. So what Herbie Flowers was paid wasn't bad, unless there'd been terrible inflation between 1967 and the early '70s. Of course it was hard to survive on £25/week in London even that long ago, but Tony managed. He didn't start making serious money until he had producer's royalties from hits he produced, especially for T.Rex and Bowie, when he could buy a nice house in London and build a studio in part of it, then later buy a second home, a Georgian mansion in the countryside closer to his wife Mary Hopkins' family in Wales.
Re Herbie's rather bitter comment toward Bowie... Much as I admire Bowie, there were plenty of times he could have been much more considerate of people he worked with, people who gave him a lot of help with his successes. The same is true of lots of stars, of course, probably most of them. Assuming Herbie's correct about how much he contributed to the sound of that track, and about Bowie not being there for any of the recording sessions, I don't think Bowie just doing the final mix was enough to offset what Herbie said. Herbie had a lot to do with that track's success.
But so did Mick Ronson.
Mick Ronson coproduced that album and played on it and probably had much more to do with its success than Bowie did:
https://en.wikipedia.org/wiki/Transformer_(Lou_Reed_album)
Mick Ronson (who was at the time the lead guitarist with Bowie's band, the Spiders from Mars) played a major role in the recording of the album at Trident Studios, London,[6] serving as the co-producer and primary session musician (contributing guitar, piano, recorder and backing vocals), as well as arranger, contributing the string arrangement for "Perfect Day". Reed lauded Ronson's contribution in the Transformer episode of the documentary series Classic Albums, praising the beauty of his work and keeping down the vocal to highlight the strings.
I have no idea what Ronson might have been paid for his work as a musician/arranger on the album (Tony had taught him a lot about producing and arranging), but if Bowie and Ronson divided the production royalties evenly, Ronson could have done very well. If Tony's original contract with T. Rex was typical, T.Rex got a 4% artist royalty to divide, while Tony got 3% as producer. I don't know what the Transformer contract was like, though, or if the production royalty was split evenly. I do know that Ronson and the other Spiders from Mars were grossly underpaid, though that was at least partly due to Bowie listening to management that eventually ripped him off badly while they lived like rock stars on his hits.