You get dedicated resources with a VPS, and
Interserver has a 1 slice VPS is $6 and you get 512mb shared memory, 25gb storage on an OpenVZ with no control panel (you could install Webmin/Virtualmin yourself or rent a CPanel install from them for $10/mo
They have shared hosting options as well as additional slices for VPS' (a slice is a share of the resources on a VPS, the more slices the more resources; you can tinker on their VPS page). Myself I have a 4 slice VPS for them which is hosting several sites (and I use a
CDN on top of that).