3e Classes have
skills on their class skill lists that can be taken 1/1 with levels. Skills not on the list cost one skill point for every half skill rank and cap at half the level of the cap for class skills.
A DM assigning a skill DC has flexibility in a number of situations despite the more in-depth guidelines of 3e compared to 5e. Some look at the expected max rank for a character of the appropriate archetypal type so a rogue detecting a trap when setting such a DC. Others suggest setting DCs so that most everybody has some sort of a reasonable shot even if they are not a skill expert in the area.
Skill DCs can easily range from 5 to 30 with characters' skill check bonuses at 20th level easily ranging from -3 to +30. Where you discretionally set DCs impacts both experts and non-experts.