I think your cost estimate for SLO is off.
The cost of attendance for a non-resident is closer to $40K. Cal Poly is a public California and relies on State tax dollars to fund the school. OOS student pay full fees.
https://financialaid.calpoly.edu/coa1718.html
The State of California cannot afford to fund non-residents. So scholarships, if any, will be really small (~2K per year).