The cost of concrete

$125.00 a cubic yard delivered 6 yd minimum. Seems to be average in these days. 24x30x.5=360/27=13.3cy 13.3x125= $1,666.67 this is without call outs for footers or Ramps.
That’s just the raw materials. Add in prep work, base, forms, etc and it is easily 3-4x that unless you do it yourself. If footers for the building are required, maybe a bit more.