if i remember correctly, there's already an income declaraction section on the green card application form to prove that u hv enough income to support for yr living. and u should hv attached 2 yr's tax returns and bank statements, etc. joint tax returns and more income will be better, but as long as it covers the minimum requirement is fine.
so, if i were u, i would ask yr attroney what additional thing he'll do for u for $250 more.
sound like he might hv forgotton to attach yr income documents (i guess ...) i don't know ... maybe i'm wrong ...