Only for 185 and 195 north facing units. So not due to lifts. Unlikely heights since I didn't read anything about levels with different heights.
My guess is that they based on past selection data and statistics to price to achieve a more uniform spread of unit selection.
From the recent 4-room selection trend, it seems that they are correct that north facing (or better view) units are more welcome, and those who select such unit are more likely to go for levels with digit '8' in it.
If they fixed the lowest and highest before adjusting these different increments at certain levels, then it is good for those who don't go for such criteria. If they start from lowest and apply such tactics, then it kind of artificially push up the prices of higher levels. I believe and hope it is the former.
I also notice that similar to 4-room pricing, the top 2 levels are the same price. Is the top level really that bad? Not even the "standard" increment of 1.4K and 1.6K for 4 and 5 room units, respectively?
Hmm I think it's because you can take both lifts at that level.
Any idea why the 18th and 19th floors have a huge increase in price for the north facing units in clementi?