From the United States, Coinbase offers purchase of USDC directly from USD (fiat) bank account. It is free. Also on the base chain, by Coinbase, any transfer of USDC to any wallet address on base chain is 100% free. If you make a pool USDC:SPS, and a bridge that uses this pool, one can move money directly from USD from the US to buy SPS. This is currently not possible in a feeless or limited fee way.