Since we're talking about early game, we'll do levels 1 - 6.
It takes about 20 - 30 seconds to run back to base from the side lane depending on your movespeed without boots. We won't count the cost or time of the TP scroll because you'll probably buy one regardless.
Also, we will ignore first blood because first blood is always far more beneficial to get. It's way more gold than a normal kill.
Creeps spawn every 30 seconds. Each wave has about 230 exp and about 190 gold. Based on the 20 - 30 seconds to run back, then TP back into lane, a hero is either going to miss 2 full waves, or 1.5 if he's lucky. So this gives us:
1. Total exp and gold cost to opponent for running back to base:
345 - 460 exp, 285 - 380 gold.
The range is actually much larger than this, because each individual creep has a range of gold given too but meh. Too lazy to count that.
2. Gold and exp gained from a kill for you:
200+(Dying Hero's Level)*9 = gold
Experience tableLevel 1: 209 gold, 240 exp
Level 2: 218 gold, 280 exp
Level 3: 227 gold, 340 exp
Level 4: 236 gold, 420 exp
Level 5: 245 gold, 520 exp
Level 6: 254 gold, 640 exp
3. Gold and exp denied to enemy from dying:
Respawn timer = 4 * Level.
Level 1: 4 seconds.
Level 2: 8 seconds.
Level 3: 12 seconds.
Level 4: 16 seconds.
Level 5: 20 seconds.
Level 6: 24 seconds.