Actually they were not that quick. They were still well over £20 for about 6 months.The TNG slimline sets dropped from this price quite quickly to £17.99 or as low as £13.99 on some instances, so I would advise to hold on a little longer
Deffo went lower quick than that, I picked up seasons 1 & 2 for £17.99 last summer and they only came out end of May.Actually they were not that quick. They were still well over £20 for about 6 months.
It's amazing how low they have got but it has taken 4 years just to get them re-released. I couldn't wait that long and got them on the year they first came out.