Well, I just won a 1946 221-1 FW as the grand prize for a 7 Quilt Shop hop here in Oregon. The shop told me was worth over $500. I also talked to a collector (chance encounter) and he also said it was probably worth over $500. He said be sure to keep it as the prices will go up in the future. It looks to be in great condtion, with the original manual. I just need to figure out what some of the attachmens are: One looks like it could be a ruffler but am not sure, as I have not seen a ruffler foot for more than 50 years.
Would not venture as guess on whether $300 is too high or not.