$20-50k is too cheap, should be about $100k now with inflation and all.
Imagine the hassle you need to going through, 3-4 years you need to keep contact maybe daily basis because gov want to check the log (print out from provider website) to make sure the marriage is legit
need photo proof as well,
also i heard they might show up on your address to check if you live together (am not sure if they announced it previously or not), so you need to keep girl clothes for in case they visit?
and in meantime you cant marry someone else within this timeframe.