What do you consider a good price? full heli coil kits are expensive either way you look at it, because they contain 18 inserts, a drill bit, tap, install tool, and tang removal tool...They also do not sell a M5/M6 kit that I know off, you would have to buy separate M5 and M6 kits...At about $70 each
Inserts themselfs are only about $1.16 each for small metric sizes, but Heli coils require special taps and install tools...That is why I do not like them..There are tons of other thread insert products that are cheaper and only require a drill and tap that I can buy for $5-10 for everything...And in my experience work just as good, sometimes better...
There is a company Coil sert that makes a product just like Heli coil but much cheaper at about $40 for a M5 or M6 kit...12 inserts per kit and includes tap and tool