The HK69 was cut along with the 40mm grenade in the early stages of Counter-Strike's development.
Its price and total carry capacity are unknown.
Weapon description files in the Counter-Strike Beta 1.0 suggest that the regular 40mm might have had an incendiary version or that it was to replace the regular 40mm cartridges.
It was not until CS:GO that players have access to incendiary devices in the series.
As Counter-Strike Beta 1.0 reused Half-Life's sprite files for ammunition, it is most likely that the 40mm grenade would have used its 20mm Grenade icon for ammunition purchase. Though as most weapons in that stage of the development, it would have likely used the generic Half-Life 9mm ammo icon for its munition count.