The only thing that really gives Strength the advantage is armor and how effective higher values can be at negating damage. If armor values weren't able to be so high I feel like Agi/Str would be much better balanced with one another. Though, heavy armor also exacerbates the one major drawback in "pure" Str builds (less than 12 for agi, I'd say 9 or less) in that they can get mobbed and taken down quite easily with less hope for clever maneuvering or retreat to friendlies. Still, the benefits of being able to tank hits and hit extremely hard outweigh the cons of mobility/cost.
I'm not really a market mastermind like POOPHAMMER but in the past two days I've managed to make up a 120k gold loss and gain an additional 75k just trading a few items around and asking for gold on top randomly (Italian Sword for Lieuyadao + gold, Liueyadao for Ashwood Pike + gold, Ashwood for War Spear + gold, War Spear for Italian Sword + Gold, Italian Sword for Military Cleaver + gold), so the cost aspect isn't really an issue except for new players (who won't have the heirlooms needed to do so), who by all means should be a bit more survivable due to their inexperience. Just lay some bait and wait for someone to bite.