Is this acceptable for the giant lizard you're talking about? Is the 200gp above a heavy warhorse (because you said a heavy horse)? I assume the lizard is considered war trained?
Giant Lizard
Large Animal
Hit Dice: 4d8+20 (38 hp)
Initiative: +1
Speed: 40 ft. (8 squares)
Armor Class: 15 (-1 size, +1 Dex, +5 natural), touch 10, flat-footed 14
Base Attack/Grapple: +3/+14
Attack: Bite +9 melee (2d6+10)
Full Attack: Bite +9 melee (2d6+10)
Space/Reach: 10 ft./5 ft.
Special Attacks: --
Special Qualities: Low-light vision
Saves: Fort +11, Ref +5, Will +2
Abilities: Str 25, Dex 13, Con 21, Int 1, Wis 12, Cha 2
Skills: Climb +7, Hide +2*, Listen +5, Move Silently +6, Spot +5, Swim +7
Feats: Alertness, Great Fortitude
Environment: Warm forests
Organization: Solitary
Combat
Giant lizards can be aggressive, using their powerful jaws to tear at prey or enemies.
Skills: Giant lizards have a +4 racial bonus on Hide and Move Silently checks. *In forested or overgrown areas, the Hide bonus improves to +8.