I’ll chime in here.
While I do not have enough experience with all the available laps out there in order to compare, I can only tell you about some overseas laps I have been working with, and depending on.
THK from e-bay.
Over a year ago, I needed to expand my preform lap options, and I found these THK laps at such a good price that I had to try them. 12 laps for $129. Actually, I think they were on sale when I bought them for <$100.
I started out with a 600 and 1200 Sierra 2 years ago. In my experience now (only 2 years) those two laps are worn beyond use. The 1200 is a nice worn-in lap for some fine pre-polish, but I rarely use it now.
With the 12 THK laps, I am able to mix-up so many grit options that I have a new faceting experience with every gem I dop up, in a very good way. I do not believe any of my THKs laps have slowed down in any way after over 100 gems of all sorts. As far as quality, I have used them for rapid preforming and pre-polishing for all my latest competition gems, with no problems what so ever. You may not have the same experience, but for $129, you will not break the bank to give them a whirl.
I especially love the 500 grit, and the 800 grit.
I was having trouble with maintaining my competition size tolerances with a cerium oxide polishing lap on very fine facets. (I have learned that Cerium oxide can actually be very aggressive). I found a very light touch on a 3000 THK did the pre-polish trick every time, then I polished quartz with a 50,000 Batt final. Again, this is for very small fine facets in quartz species.