Salt prices varied a lot by region, due to the different distances salt needed to be transported, different transport costs (ship vs land), and taxation. For example, Miller (1991) discusses the variation in English salt prices in the 13th to 15th centuries. For most of this time, salt was cheaper than wheat, per bushel, varying from 58% of the price of wheat to exceeding the price of wheat in the most expensive two decades (the 1380s and 1440s). The highest prices were in the regions furthest from salt-producing areas; the highest prices were almost double the lowest prices. Scottish prices for salt were approximately the same as the price of wheat, for the 13th and 14th centuries (Gemmill and Mayhew, 1995).

Also note that salt being about the same price as wheat wasn't unusual - the Roman Price Edict of Diocletian listed similar prices for salt and wheat. This means that salt wasn't an extremely valuable product.

Where salt was expensive - where it had to be imported and transport costs were high, it could be much more expensive. For example, in Sweden, salt was about 10 times the price of grain in the late 13th century, dropping to about double the price of grain by the early 16th century due to dropping transport costs (Söderberg, 2007).

Salt could be heavily taxed. Taxes could more than double the price in a region. Taxes like this sometimes led to great variation in prices in adjacent regions, which drove a sometimes thriving smuggling trade, in turn sometimes leading to strong attempts to suppress smuggling. In extreme (post-Medieval) cases, salt taxes could drive the price of salt much, much higher. For example, in Provence in 1710, the salt taxes were so high that the cost to the public was 140 times the cost of production (Laszlo, 2001); prices this high made it unavailable in sufficient amounts to use for salting meat for preservation for many people.

I don't know if there was equally extreme taxation anywhere in Medieval Europe. But transport costs alone caused a variation in prices of at least a factor of 20 (from about half the price of wheat to about 10 times the price of wheat). Where it was cheap, it was easily affordable. Where it was expensive, it would still have been readily affordable for regular use in cooking - what might have been too expensive was the large amounts needed for salting fish or meat.

References:

Elizabeth Gemmill, Nicholas Mayhew, Changing Values in Medieval Scotland: A Study of Prices, Money, and Weights and Measures, Cambridge University Press, 1995

Laszlo, Pierre, Salt: Grain of Life, Columbia University Press, 2001.

Edward Miller, The Agrarian History of England and Wales: Volume III 1348-1500, Cambridge University Press, 1991

Johan Söderberg (2007), "Prices and Economic Change in Medieval Sweden", Scandinavian Economic History Review, 55:2, 128-152, DOI: 10.1080/03585520701435988