If you got a FW table for $100, I'd have said you did very good. If you had got the 301 long bed table, it would still have been a decent deal. The one you have is probably the one that sells for the least of the three - but $100 for it is still not outrageous. BTW- it also fits the 301 short bed.
It really has nothing to do with rarity- it has to do with there being a lot of people that want a table for a FW, and not many that want any of the others. So even though the FW tables are the most common, they also typically sell for the most $$$. The rarest is the one that fits a full size bentwood case bottom - but they don't have much market except to collectors.