The rebar is 2X the price of buying locally at Lowe’s ($2.48 for 4 ft —> $0.62/ft). Personally I don’t typically use rebar for Blacksmithing: it’s kind of mystery steel and too variable in hardness.
The O1 steel is probably good for stock-removal knife-making purposes, but buying precision ground steel just to heat, beat, and repeat (eg blacksmithing) is probably not warranted. Hot-rolled non-annealed is fine for Blacksmithing.
$0.93 per railroad spike is not a bad price. $1/spike is common at flea markets and Amazon is certainly more convenient (assuming you need 75 of them).