Visi, Human Expert 2/Human Paragon 2
7 ranks in Balance and jump. Dodge, mobility, roof-walker and roof-jumper as feats.
18 STR, 18 Dex, nothing else matters.
Now, a warning eager shuriken (say 400 gp?) gets an extra +7 to INIT, along with the aggressive trait for a base of +13.
Contingent Dimension door, 2800 gold.
Contingent Wraithstrike, 600 gold.
Contingent Nerveskitter, 100 gold.
Contingent True Strike, 100 gold.
A single casting of fly will cost us 150 gp.
Let's also get a casting of Cat's grace before hand too. For this purpose, it will cost 140 gp (CL 7).
That's +20 to initiative, and dropping in on him from (3000 - (1d6 x60) ) feet, or a minimum of 2640 feet. Thanks to Roof-Jumper, that gives an extra 264d6 damage, which averages to 924.
Total gold spent, 4290 gp of 5400 gp. Total ECL 4.
Chance of winning Initiative, with a +9 lead on him, 86.3%, if the source I found is correct.
Chance of hitting, with +2 BAB, +4 STR, and +20 from true Strike, total +26, against AC 16, is 95% due to chance of auto-fail.
Chance of doing 305 damage with 1d8 (weapon) + 6 (two-hand STR) + 264d6, Incredibly high, assumed 99%, probably better.
Chance of surviving, thanks to Dimension door, is 100 %.
Total chance of success, 81.16515%.
Exp gained if successful, by extrapolating the tables in DMG as instructed, is 307200.
Total exp assuming minimum for level 4 at start, 313200 xp. Level afterwards, half-way between 25 and 26.
The 80,000 gp the DMG recommends for killing a blaor will also more than cover the just over 4000 spent.