I am doing it myself as we speak and I am in Southern CA. Bought all the parts this weekend. Fortunately, my location is 2' feet away from my main panel. Total cost.
50 AMP breaker: $9.48
4' 6/3 cable: $12.00 ($3 per ft)
4' 3/4" flex conduit: $4.00 ($1 per ft)
3 pack connectors conduit connector: $3.50
Wiring caps: $3.98.
Total: $32.96 + tax
Maybe add $10 for some weather sealant caulk and patching material.
If I was running 100', almost all your cost will be in wiring and conduit. Couple of junction boxes, materials should be about $450.
I am not an electrician but have some electrical/mechanical training and experience. Electrician can charge $60-$100 per hour and I think it'll be a 8 hr day's work for 100', at most. $1,000 is reasonable but $1500 is too much.