S'mon said:
I'm a bit sceptical of the 50% taxation figure for villeins, I suspect it depends largely on how you quantify eg working on the lord's fields. I've pretty much excluded that sort of non-pecuniary feudal service from my model on the basis that at most it provides enough food to maintain the inhabitants of the castle, not a surplus that can be sold for new armour, weapons and the stuff players care about.
The "economic and social history" book I was talking about in my post above supports your position on this. The author made the claim (although I'm not completely convinced) that a lack of ability to turn surplus into cash kept manor lords from exploiting their peasants to the degree that later slave systems did in more efficient capitalist environments. His basic point was "why would a lord make his peasants work harder if he was just going to have to eat all of the produce anyway."
The 5 sp/person figure you use is similar to what I use (in my case it's based on the 1E rules - I think, it's been a long time). That figure does a pretty good job of the lord breaking even as follows:
Typical Manor (monthly totals):
Manor income: 336 gp (420 person manor; 8 sp/month/person)
Tax to overlord: -50 gp
2 mounted seargents: -30.4 gp each
3 archers: -3.8 gp each
upkeep for knight and family: -50 gp
horse upkeep: -30 gp (heavy warhorse plus some riding horses)
manor maintenance: -20 gp (ballpark figure for 1/2% of large stone building plus grounds)
reeve and officials: -36 gp
bailiff: -36 gp
This leaves 41.8 gp/mo surplus which my NPC knights fritter away on miscellaneous expenses - probably pushing their "upkeep" figure closer to 100 gp which matches one of the higher upkeep values in the 3E DMG.
I assume additional boon work, fines, etc. cover any miscellaneous expenses that I've forgotten. Comments are welcome.
