My husband and I took the half-day tour to the Postojna Caves and Castle. My main criticism of the tour is the deceptive advertising. The price on the brochure is listed in large letters as 68 euros. While en route to the cave, I was taken aback when our driver asked if we had paid the entrance fee yet. I thought we had, but when I looked again at the brochure I had brought with me, I saw that I had failed to read the fine print - the entrance to the caves and caste is an additional 35 euros. Fortunately, we were able to pay for the entrance fees over the phone with the Roundabout Travel office, which tells me that we were not the first people who failed to read the fine print. I could understand if you are selling a tour to a site (such as Bled) where there are things to do (admire the scenery, take a stroll or have a snack) that don't necessarily involve taking in an attraction, then by all means advertise the cost of the transportation. On the other hand, if you are advertising a tour that has no other purpose than to see the site you're going to (such as the Postojna caves and castle), then include the entrance fee in your total - unless you think that total is too high and will turn people away. Better to lure them with the 68 euros and then sock them with the additional 35 when they have no other option but to pay it.
Cost aside, the van arrived on time and our driver was pleasant and efficient at directing us to where we needed to be once we arrived at the caves. We arrived about a half hour ahead of the 10:00 tour so there was a little time to shop if desired or use the restroom. After the caves we had a short drive to the castle. We had a little less than an hour to spend at the castle and could have used maybe an hour and half, but I understand that given the time constraints of the half-day tour, this is about all the time that could be allowed. As it was, we hit traffic on the highway back to Ljubljana and arrived about a half hour later than 2:00 time that was advertised, but that was not the driver's fault, and the time was not an issue for us.
In summary, if you have no other way to get to the caves and castle, this is an efficient way to do it and you will get to see enough to make the visit worthwhile. The Postojna caves are a marvel, and the castle is quite interesting. Just be sure to read the fine print.