Kami described them as having only half the power of "full-fledged Saiyans" so it all depends on what metric he's using. If Raditz is being treat as the benchmark, then they probably wouldn't be much higher than 600-700. It's possible they may be higher when they considered higher when considering they scoffed at a group of 4 people at a total battle power of 1,507, so either they were confident in simply picking the group off one by one or Kami has more intel on what Saiyans can be capable of via his Other World connections. That could be likely when considering the Daizenshuu states they're immature second-rate warriors whilst describing Raditz's power as the bottom of the barrel for a typical Saiyan.
Official sources contradict what the anime has to say when it comes to rating them. The DBZ Movie 3 pamplet places them at 3k, which is far too high, whereas their counterparts in the game Kyoshu! Saiya-jin are seemingly too low ranging from 400-500.