Outdoor extension cord for under house wiring?

[GTPXAZ]

I want to add a 30 amp RV outlet to one end of my house.
My Breaker panel is at the other end of my house (about 75 feet away)
10/3 wire has gotten ridiculously expensive (10/3 romex is over $4/ft).
Is there any reason I shouldn't use a 10 gauge 3 wire outdoor extension cord for the run under the house (crawl space)?
I can get the extension cord for just over $1/ft.

 

[Megawatt]

I want to add a 30 amp RV outlet to one end of my house.
My Breaker panel is at the other end of my house (about 75 feet away)
10/3 wire has gotten ridiculously expensive (10/3 romex is over $4/ft).
Is there any reason I shouldn't use a 10 gauge 3 wire outdoor extension cord for the run under the house (crawl space)?
I can get the extension cord for just over $1/ft.

Sure you can use the drop cord but it needs to be rated at 30 amps with ground and also be outdoor approved/wet locations. It also needs to be GFCI protected.