It depends what lv x and what EX
remember training rotated cards (EXs) for lvl xs may be tricky may be a 2-3 ratio for a non playable to playable card.
DEPENDING on the $ value. Also depends what time of year too.
example:
Charizard ex Can go for $80+
Wailord EX can go for $40
Wigglytuff ex: $4
lv x examples:
Cresslia ex: $35
Any Tin lv x card $7