If you're having problems modifying your game on your own, use this mod, [url="http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=1906"]Richer Creeper[/url]. It gives him 200,000 gold and I believe it increases what items he will buy.
If you want to do it manually, I recommend killing a few Ordinators in Vivec: (spoiler)
Transport to the Mage's Guild in Vivec, go right outside the Mage's Guild and in that small area there is a single Ordinator. All you need is a bow and a melee weapon (bound items are best if you don't have a really good weapon, long weapons are better). There is a flower bed that you can hide behind where the Ordinator won't be able to reach you. Get behind the flower bed, shoot him with your bow and he will run up to you. Just hack away with your melee weapon and eventually he will die. Drop ALL of your stolen items and go outside to turn yourself into another Ordinator. It will only take about 35 gold to remove the bounty from your head, but he will also take any stolen items you are holding including anything you took from the dead Ordinator's body. Once you remove your bounty go back and get everything from the body. Head back to Caldera and go to the armourer next to Creeper's house. Repair all of the Ordinators equipment (otherwise it won't be full price and trading items worth exactly 2k, 3k, 5k, 7k is much nicer).
The Ordinator gear has a couple items worth 2,000, a couple worth 3,000 one worth 5,000 and one worth 7,000. Before you try this, make a completely separate save game so that you don't accidentally die or get all the ordinators trying to kill you.
Once you have a few pieces of gear to sell in the 2,000 - 10,000 gold range head back to Creeper. It works like this:
- Starting: Creeper has 5,000 gold.
- Sell him an item or items that add up to 5,000 or close to it.
- Creeper now has items worth about 5,000 but no gold.
- Click rest, it will say you can't rest you can only wait, so wait for 24 hours (you can do this right next to Creeper you don't need to find a bed).
- Creeper now has the items worth ~5,000 and he has 5,000 gold again.
- Sell him something worth 10,000 gold and buy back 5,000 worth of items at the same time. You are giving Creeper an item worth 10,000 and getting back 5,000 in gold and 5,000 in items. Creeper now has an item worth 10,000 and no gold.
- Wait for 24 hours again. Creeper will now have an item worth 10,000 and 5,000 gold.
- Now sell him the items worth 5,000 again.
- At this point Creeper will have items worth a total of 15,000 and you will have made 15,000 gold. You can continue to do this until you can sell your 60k soul gem but you need to have enough items that Creeper will have 55,000 gold worth of items or you will lose money. (You would be selling 60k soul gem for 5k gold + 55k worth of items then you have to go through the whole thing to sell all the 55k of items back).
Personally I think it is much easier to get a richer creeper so you can sell all at once.