I suck at it too because I get greedy since it's not real money.
If you totaled the 26 suitcases you'd get $3,418,416.01 equally on average $131,477.53 per suitcase. So, if I were playing for real I'd make a deal at about $130k if I still had two big suitcase up, e.g. 500k and $1 mil. If not I'd try to settle for $50-60k.