A subsistence farmer with his family, animals and seed supply is high-volume, low-value goods compared to some other trade goods. With expensive small knarrs, emigrants may take the trips like Norway-Iceland, or Iceland-Greenland, or Iceland-Vinland - but from Europe direct to Vinland, whether islandhopping or straight over empty ocean, gets too expensive even with 13th century population pressures. And that would hold until better and cheaper ships come along in 17th century.
Precisely why better and bigger ships would be developed earlier than OTL. As you mentioned in the other Vinland colony thread, "In OTL, Germans developed bigger, more efficient cogs in 12th, 13th century. If Vinland trade increases, they could not just take over the cog - it is a solution for a different task - but developing a bigger ship adapted to crossing empty North Atlantic may make sense."
Pre-Black Death Europe not only had population pressures, it had a plethora of younger sons of nobility who lacked the Crusades to draw them away and kill them off. Once news of this new land across the Atlantic spreads -- and it certainly will -- second sons will be lining up for ships that will take them to a land where they can create a new class of landed gentry. They will need larger ships to carry supplies and the settlers to create their new estates. (Happened in Colonial America, too, but could be more likely to succeed in an earlier time.)
There was a reason why 16th century Spaniards picked the populous Central and Southern America where they could conquer and exploit Indians, and ignored the less densely settled areas like North America. Only in 17th century did English start farming settlement.
Yup. Gold AND slaves.
A settlement of a few hundred Norse on a small patch of Newfoundland might be sustainable - yet keep growing over centuries because of natural increase, continuous trickle of immigrants from Greenland and Iceland, and interbreeding with Skraelings.
And the trade all the way to Europe would be limited to high value, low volume goods - including a few passengers.
As the settlement expands further south to warmer climates, the few immigrants who come from, say, Ireland or England or Germany may introduce warmer climate crops like wheat or vines (Leif had a German in his crew who knew vines). But they would still be few, and they would soon teach the use of wheat to their neighbouring Norse, and also Skraelings.
When the population of Vinland grows and the demand for low volume, high value trade to Europe increases, yes, it creates incentive for better ships.