Answering two questions.
I hate to say it but I have seen clean great condition P25's for as low as $10k. THe minute they become available retailers snap them up. The reason the cost is so high is because there are not that many out there. Phase did great as well by giving us back so much for the back to upgrade to a P45. So the few used P25's usually come from retailers for only $5k less than the P45. I would continue to hunt them down and you may get lucky. There was one in NYC for a Contax mount on a site called Craigslist for $12k a few weeks ago.
On the Valeo front. I would not pay more than $5k for one of those. It has no screen and only shoots to caddy or tethered. if you can live with that then it is a great deal. I need a CF card slot and a screen to look at. No matter how bad the screen, at least I have a HISTO to look at.
If you are using your back on an RZ I would not buy a universal mount. What I would do is think long and hard what kind of 645 you may grow into. Whether that be the H1 or 645AFD II. Then buy that mount on your medium format back. Next go to www.eco-digital.com
and by the adapter plate. If you are buying it for the H1 you have to go to Eco, if you buy it for the 645AFD II you can get a plate from Mamiya. it will also serve you better for resale in the future. As long as you are not a Hassy V series shooter.
If you are having problems getting an A75back in the great white north. Call them direct and don't settle. Call Leaf America in NY and check with them. Kevin Stuts is a great point of contact and is very helpful at Leaf. If you are serious buyer he will bend over backwards to make sure you get your time with the back. Unfortunately, I do not support the two NYC Leaf retailers. But there is a great company in Philly called Webb Photo. I may go through them as soon as I figure it all out.
They may even fly up to help you out. Ask for John or Dan at Webb.
On the Phase to Leaf front. I love my P25 but the high ISO I was not a fan of and I rarely shot at less than 250ASA in the film days. So it was tough with a ton of KINO and strobe lately. C1 pro is amazing and there is no better processing software. The leaf files were sharp, warm and looked like 100 at 400. 800 looked like MF 400 rated at 250 and with some tweaking it is amazing.
I have not had the chance to play with P45 at 400. So I can't say about that. But that it doesn't shoot at 800 killed it for me, the size of the files are insane and I like the ability to pump it to 800 if I needed it. We don't need that file size. Wish I could afford to keep the P25 and get an A75, but I cannot. I have a deal on the table with someone for $16.5K for my P25. We will see what happens. Leaf will give you a loaner A22 until your A75 comes in when you buy.
Hope this answers some of your question.