A level 100 player on speed 1 will have collected the same amount of gold, and the same amount of orange/red items, as the same player on speed 5. He just collects it slower, as he advances slower in levels as well.
I agree with the loot. But you forgot the smelting time..
And that's only orange and on a x4 server. x1 would have around 56 hours, while x5 would have around 11 hours..
Let's say you have orange helms of lvl 110-115 with an event that gives you 10% more mats, x1 speed will smelt one in around 15 hours, while x5 in 3 hours.. That means x1 smelts 6 items (Or 12 if they put a day before) while x5 smelts 48 items (Or 56 if they put a day before)
That's the biggest difference in speed servers.