i want to get phoenix wright, but the console based account system makes me really dont want to spend too much on the eShop.. i want to wait for a sale, do they often have sales on eShop games?

as far as i remember so far only those game that is under 10 dolar got discount ... you can wait for it no promise ace attorney will in the discount list...
if you really wan to do ace attorney good i suggest you purchase when it release show capcom there's love for the series or they might thought that it's not worth to release ace attorney game in english...
ace attorney investigation 2 never see daylight untill now

those nintendo retail game available on eshop rarely got sales one. but some of the third party games is priced cheaper, especially capcom punya resident evil series, just 19usd. nintendo games such as mario kart 7 still 39usd last i checked.

got sales punya most is eshop title, pushmo, those retro titles etc.

Rarely any Nintendo games gets sales. Most games that are below 10 or 5 dollars does go on sale sometimes. It's not like PSN, at day 1 also got sales already.

waiting for Starship Damrey price cut sales

Pokedex 3D Pro cut from 14.99 to 9.99 during April I think
Too bad I miss it too lol