These are his stats:
If he was smart, he's probably have a few phats sets, crackers, masks etc.
So going off of that, I'd say 3 grand+. But if you base it just off of his stats and nothing else, 30$ max. 300+ for being the first person to join the game. It's worth more or less depending on how you value being the first person to join RS.
Overall 1,163,648 1,122 15,330,933
Attack 72 949,415
Defence 65 478,768
Strength 80 2,044,221
Constitution 74 1,138,105
Ranged Not Ranked
Prayer 52 135,025
Magic 70 800,118
Cooking 65 494,030
Woodcutting 92 6,573,326
Fletching 53 136,779
Fishing 65 460,830
Firemaking 55 181,286
Crafting 59 255,443
Smithing 52 128,727
Mining 66 507,372
Herblore 69 687,948
Agility Not Ranked
Thieving 57 214,574
Slayer Not Ranked
Farming Not Ranked
Runecrafting Not Ranked
Hunter Not Ranked
Construction Not Ranked
Summoning Not Ranked
Dungeoneering Not Ranked