For the sake of the current discussion, I'm not sure the sources or accuracy of this article, but it places the estimate of the entire TNG remaster at "north of $20 million."
Cost has been raised as a factor. The original series Blu-Ray releases were extremely popular, selling very well on Blu-Ray and doing well in streaming. TNG started off very well, with strong sales, but tailed off significantly over the course of its run. The cost of the remastering was substantial, with some reports placing the initial set-up and start-up costs, plus the cost of remastering the first season, at over $9 million. Later seasons came down substantially in cost as the team became faster and more proficient, but additional cost savings (such as farming some of the work out to third parties) were lost due to quality issues (the quality of the second season's remastering, handled by an outside company, is notably inferior to the other six). The total cost of remastering all seven seasons has been put at north of $20 million.