If the girl really liked the guy, she wouldn't care about the ring. If the guy really liked the girl, he wouldn't give up on her just because he was too cheap to buy a ring the girl liked. Works both ways BoB!
But yeah, something about going to a store and having a guy point at the cheapest one and going, "THAT'S the one you're getting" is really really really not appealing.I mean, dang man. That's just soo... I'd probably either crack up laughing or start crying. Or both. xD
If you can't afford to buy a ring, as your mother/grandmother if you can have their engagement ring. At least that way you can pass it off as being romantic and sentimental rather than just plain cheap.