After 40 some years of cutting for pleasure, competition, and business, I recently got toppers from a reputable dealer – 180, 260, 600 and 1200 (to see if they were worth anything). If you are trying to get accurate/non-frustrating faceting, stay away!!! Even bolted down to a good flat master lap, they have some wobble. Nothing more frustrating to a beginner than not being able to get facets to meet with the stuff someone recommended to them. I saw this first hand while teaching a first timer who had the suggested economy disks.
If you want to cut corners on price, use toppers for the coarse grits, 100 – 360. Other than that, for the laps where you want the meets too MEET, get some good, FLAT backed disks. Otherwise, all your fancy, accurate machines and gauges are all for naught.
If you are in this for the long haul, 600 and/or 1200 grit sintered laps are worth every penny. Sorry I only took that dive after 40 years of using metal bonded disks for their relatively short useful life.