If conjure (summon) animal was scored like a DM designed encounter for the PC to overcome, here are the xp. budget costs for the different options, 1 Cr2 450xp, 2 Cr1 600xp, 4 Cr1/2 800xp, and 8 Cr1/4 1000xp.
A more balanced approach using the encounter building budget xp. costs would be, 1 Cr2...