How many miles on the vehicle?
I for one would replace the transmission oil with new Lifetime 6 oil. Go to
The CTSC - ZF Parts and make sure your transmission takes Lifetime 6, but I'm pretty sure it does. There's a special fill procedure (can be found here by searching). You're right, transmission is the first priority.
If it is an outer boot, he's a bit high in my opinion. There's a 30 minute DIY on this site. If it is the inner boot, then it may be fair. 2nd priority fix.
Subframe bushings are a pain to do without the right tools. By the estimate there, I am not sure he has the right tools, though I don't know how much the bushings cost. I think I could easily do it in 7.5 hours with the right tools. There's a DIY on here where they put in powerflex bushings instead of stock. 3rd priority.
Might be worth a second opinion just to see if the prices are fair if you have another european car specialist near you.