Simple supply and demand explains that when demand is higher than the supply, the price goes up. If demand and price remain high, then the supply will surely increase. Eventually, supply is increased to meet demand and the price settles to its "natural" level.
The story we are repeatedly told is that ammo manufacturers have maxed-out their current production lines, making as much ammo as they can. Increasing production beyond that requires adding production lines of expensive equipment, that would need to be run for years in order to recoup the setup cost. But they say that the demand spike is caused by fear from various gun-control related events, and that it's made worse by hoarders buying it all up. They all say that this is temporary demand and doesn't justify expanding production.
How long do you buy their "temporary" excuse? The current anti-gun President has been in office for FIVE YEARS, and there have been multiple events that trigger a renewed gun control uproar during that time.