Depends. If someone went all-physical for their games then wouldn't a $20 4GB card be enough? I'd imagine that people going for the lowest possible prices would be buying physical carts (that they can trade-in or sell later). So for that type of customer, $20 on a memory card is a one-time expense. Or "free" if they buy a bundle.
Now for convenience, the 32GB card is the best choice. Expensive at $80-$100 but if you're buying all-digital then you're already on a different spending tier. For that kind of customer, convenience justifies the extra expense so $80 for a card is a pain but they're already looking to spend hundreds of dollars on digital games that they'll never be able to sell or trade-in.
(This is me. I've spent a lot on digital games. I'm past the point of caring about the $80 I spent on my 32GB card.)
TL;DR: Memory card prices is just a rationalization held by people not interested in the Vita in the first place. Price-sensitive gamers will prefer physical carts anyway and you don't need more than a $20 4GB card to go that route.
I can see your point, but for me it's actually a pretty big reason. I'm a PS+ user so I'll naturally need a big memory card. I can't see myself NOT buying a 32 gigs card for my European account, I'm sure you can agree with this. You're talking about how buying game carts is the cheapest way to go, but I'd say PS+ is... And requires you to have a big cart to enjoy it, unless you're okay with the unconvenience of having to constantly install/uninstall games.
And then I have my Japanese one. I play a lot of Japanese games (and kind of live in Japan), and it doesn't work like the PS3, where you can change accounts easily and any installed DLC is made available to every user on the system, regardless of the region of the PS account tied to it. So while I can play Japanese game cards with my EU card, any game using DLC would be busted (a friend of mine got stuck like that with Soul Sacrifice, he bought the Japanese version since we live here, but he uses a EU account. He realized he couldn't use the product code for the multiplayer after putting 20 hours into a save tied to his EU account, and thus unsalvageable).
So I need a second memory card for my JP account. Considering the price, I won't buy another 32 gigs, but 16 seems like the minimum since I want to play PSO2, that would gobble over half the space on a 8 gigs (for now! It'll definitely grow in size as updates keep coming by).
Sooooo, that leaves the damage count at somewhere from 15 000 (absolute lowest for used wifi model with some scratches) to 20 000 yen (new machine) for the system, plus something like 12 000 for the cards. About two thirds of the system price!
I really want to buy a Vita and I'm totally about to cave in for various reasons (I'm just waiting for a potential new model announcement at E3, you never know), but the memory card price is by far and large my biggest beef when I think about that purchase.
Disclaimer: I realize this is MY particular story and tons of people do not need a second card. Also, some of my arguments are purely convenience-related.
But this is GAF, where I'm sure a lot of people will want to use at least two accounts. Especially people (again, like me) who were spoiled by how easy it was to switch on PS3 and download or bought all kind of stuff on other regions' stores. Effing IGN had a video tutorial about how to change regions...
I know, it's a problem of mine. In any case, I would probably buy more games even if I had Plus, so I'd end up spending even more than now for games in the long run. I'm still a student and will be jobless for at the very least one more year, so maybe someday I'll be able to pay for both games I want and Plus free games, but unfortunately that time is not now 
