I should mention that a lot of the really cheap (10-15 NT each) cards fall into the ‘cutsy’ category and are aimed at younger folks. Granted, this is where you’ll find some truly funky and creative stuff. Personally, I LOVE the use of a variety of paper types, inks, folding techniques, etc, so I buy a lot of cards from this lot. You can also find some of the more standard message cards in the cheap lot, but with a bit of flair thrown in for good measure. Plus, a lot of these contain a blank card inside, so you can write whatever message you want. Personally, I prefer this over a canned, melodramatic, mushy message written by who knows who in a Hallmark greetings card sweatshop in lower Indiana.
If you want something a bit ‘older’ and more ‘sophisticated’ in a traditional sense, those are also out there. Hallmark type cards can be had for 35-40 NT each. The selection I bought were 35 NT each, with an elegant design and use of multiple ink types on high quality paper stock to create a very attractive effect. Plus they were slightly oversized. (An equivalent Hallmark card would cost around 120 NT.)
By the way, the Eslite I mentioned on Wen Lin (near the Shihlin MRT station) has a decent selection of all varieties of cards.