I don't think so either. The last time he was captured (in order to get the Tortured virtue), I believe he only cost about 2000 florins to ransom back. He was lower valour back then though. The 870000 florins listed in the logfile is probably the cost to have a single valour 25 knight in MP.

As far as I can tell, the maximum valour a general can have is valour 32 (+19 from virtues, +4 from having at least 8 command stars, and +9 from combat experience), so Lord d'Anghiera is at 78% of the maximum.

Btw, those valour-granting traits apply to all the knights in the general's unit. So if I should take d'Anghiera and retrain him, adding 19 knights to his unit, those fresh knights will all start at valour 16 (+12 from general's V&V, +4 from command), even though they have never engaged in combat.