Steam has rules intended to curb this behavior.

partner.steamgames.com/doc/marketing/discounts

Specific Discounting Rules

You can run a launch discount, but once your launch discount ends, you cannot run any other discounts for 30 days.
It is not possible to discount your product for 30 days following a price increase in any currency.
Discounts cannot be run within 30 days of your prior discount, with the exception of Steam-wide seasonal events.
Discounts for seasonal sale events cannot be run within 30 days of releasing your title, within 30 days from when your launch discount ends, or within 30 days of a price increase in any currency.
You may not change your price while a promotion is currently live or scheduled for the future.
It is not possible to discount a product by more than 90% or less than 10%.
it is not possible to create new discounts for a product that would result in the price in any currency falling below Steam's minimum possible transaction price. See details.
Custom discounts cannot last longer than two weeks, or run for shorter than 1 day.