Well, I'll speak a little counter to everyone else's response here.
For starters, when I say 'cheap' I don't mean *too* cheap, because I only use toys that are silicone, glass, plastic, wood, metal, or something else non-porous. So, no cheap jelly or rubber or TPR.
So, that said---I also haven't tried too many vibrators. I've tried the
All Night Long (list price probably around $20---EF decided not to stock it)
Spoon (list price $28)
Reflections Beauty (list price $33)
Shello (list price $54)
Vuali (list price $70)
The Cone (list price $120)
Ina (list price $156)
Wow, that was a really interesting exercise. Of these, I'm not going to include the Cone (because it's in a whole different category---worth the money but it's not the kind of vibe you were asking about) and the Spoon (it's a bullet, and it's great for me, but again, it's not like there are "luxury bullets")
Clit vibes don't count: Cone, Spoon.
So---I have pretty strong pelvic muscles. And I found out that my pelvic muscles can stop some vibes from vibrating when I'm getting close to orgasm and I "clamp down."
The vibes that I cannot stop: All Night Long, Beauty, Shello.
The vibe I can slow down: Vuali.
The vibe I can stop altogether: Ina.
So... higher price doesn't necessarily mean stronger motor. Part of it also is the structure of the vibe---Shello is a really delicious combination of firm and flexible (sunshineamine shows good pictures in her review), while Vuali is stronger than Shello, but it doesn't have much structure or support where my muscles clamp, so the motor suffers. Ina... there is no excuse for Ina, it's got a hard plastic core. I was really sad about its performance. All Night Long and Beauty are firm materials, so there's no way to deaden the vibrations.
So---it's not just "spend more money and you'll get a better toy." Spend *enough* money to get safe materials, definitely yes. But it's important to really consider the shape, the design, the construction, and how it will work for you, before deciding to spend money.