Well, I had issues of many parts needed that weren't planned on. I couldn't use the jdm climate control, so I had to fork out $400 to get my AC working, plus my pedal assembly had to be swapped to accomodate the jdm parts, the jdm radiator was too big, so new parts were needed so it would fit, I got a TD04 instead of a TD05 on my engine, so I had to buy a second hand TD05 from New Zealand. Shipping for the front clip burned me bad and taught me a lesson to get quotes in writing, as I was told it would be "around $500" COD, but unforseen circumstances made it $1200 when it arrived, and they said it either I pay up, or my shipment is destroyed
I got them down to $1010, then to $805, and called that good.
Christoph, I think the jdm route is the main reason for us saying have 50% more cash on hand, just in case. You seem to have the USDM WRX swaps you're doing down to a science, so maybe this doesn't apply as much.