I would budget $5-600 for a nice set of soft doors. By diligently watching the various websites, you'll likely come in just under that. A set of used (faded or needs stitching) will likely be $75-100 per door.
I find it funny with everyone complaining about or questioning the price of X-doors (hard doors). They're an item that aren't being made anymore, aren't regularly being made available via auction and the demand for them has surged. $2000 is about the going rate anymore for them. I've sold 3 sets that I've come across for roughly the same price without sitting on them for long. Ya might get lucky and spend less, but I don't see the prices of armament carrier stuff getting any cheaper like it was pre-Iron Planet days.
While your typical mechanical parts are still readily available for reasonable prices, or there are commercial alternatives to those items - when it comes to the roof, doors, etc., the prices have all jumped considerably. My understanding is that the company that made the soft tops and doors for the military is out of business and anything that's for an armament carrier doesn't come up very often. As a result, the supply is low and the demand is exceptionally high.