I have seen floridas and spotteds going at about that price @ 6-8".
I have been lucky in regards to fish lice, I have had one fish that had two lice (argulus) that I picked off with tweezers during quarantine. They are tough little pests but I have heard that there are several praziquantel based products that kill them.
The most interesting cure for infested fish that I have read about is simple heat. Most argulus sp. apparently die off at around 86 degrees F. so they reccomend slowly raising your tank temp to between 88-90 degrees and adding some surface flow, leave the temp at that level for at least ten days, the articles said that this treatment might need to be repeated after a week. They also advise physically removing all that you can, pull them off like you would a tick, no twisting motion, just a firm, steady, straight pull. A dab of iodine one the wound does not hurt either.