OK, so shall we agree on DC12 Craft (alchemy) and Craft (leatherworking) checks, plus the spells animate dead and bull's strength suggested by freyar? Add in Craft Construct, a gray ooze and a corpse and I think that's enough for the prereqs, which only leaves creation cost.
Well they're not that tough, so I guess somewhere in the low thousands of gold pieces? A flesh golem is about 10,500 gp for a creature that's CR7, HD9 and has that golem immunity to magic, so maybe a bit lower.
Caster Level 5?
3000 gp and 200 XP? 2000gp and 150 XP?
That looks a bit cheap, but if they're uncontrollable what use are they?
Hmm, if you actually have to have the ooze, I guess there's no need for acid arrow or similar spells, so that's a reasonable list of prereqs. I could see 3000 gp, 200 XP if everyone agrees.