Bitcoin can not be difficult to purchase. Even 1 sat is relevant. If bitcoin become scarce and its price increases, the quantity that individuals will purchase will be small because of the high price but everything will be normal as usual as they will still be able to purchase the right amount that they want to purchase.
Lots of people and now entities, governments following suit as well, are holding bitcoin but not all of these will be holding bitcoin all the time. Some individuals might want to sell for profit or maybe use it to purchase something. So, no need to worry about not being able to buy. However, it will be difficult only because the demand for each sat or bitcoin would be extremely high and you might need enough funds to do so.
It can be reduced as well if the concept of bitcoin being a currency instead of an asset to be held was strengthened. Lots of bitcoin enthusiasts are pushing for bitcoin to be a mainstream currency in many countries.