Item Building, please help

[caith]

Hi!

Ok here's the deal: My DM has a system where we can use experience to purchase items, currently im trying to buy two items, they must be valued under 20k. I can't really find anything that fits my uses so I am begging: please help!
I have two questions:
1. Are these items too expensive, why, and how do i balance them to cost less than 20k
2. Are there equivalent items that cost under 20k that i could present to my DM
i'm trying not to be a power gamer - it's not in my nature, but i want to get the full value out of my hard earned experience, while not arguing terribly with my DM, and i am somewhat unsure of the rules, and wish to politely disagree

Here are the items, at the level that i think is fair:
Cave Dweller's Sword 1d6+3, 3lb., 19306gp
Short Sword - 6gp
Masterwork - 300gp
Use Activated "Light" Spell - +1000gp
+3 Attack Bonus - +18000gp
he says the light spell would add a +1 market value but i am unsure, i cant find good spell value literature, but would accept a +2 attack bonus

Shadebeast's Hide +4 AR, MD +5, 15lb, 18575 gp
Studded Leather Armor - 25gp
Masterwork - 150gp
+10 Sneak(a variant skill that rolls hide and move silently) - +15000(to account for both skills?)
+1 Armor Bonus - +1 value bonus - +1000
Invisibility, 1/day - +2400
again i am unsure if the invisibility adds a value bonus in addition to it's cost

thanks for the advice!

[_Puppetmaster_]

actually, you can make any magic weapon so that it glows all the time at no extra cost.

[Randel]

As for the Light spell, according to the SRD about 1 in 3 magic weapons already glow as if with a light spell. It shouldn't take much more than say 100 or 500 gp to make the light switch on and off as you command.