A developer that is working on a site for me is using ghostscript, codeignitor and imagemagik. A hosting company has told him that those will be a resource hog and that he should use a dedicated box. I think the sales guy is just trying to upsell. A managed VPs is more inline with our budget.
Anyone have any thoughts?
Depends on how much traffic you have, hence how much concurrent use are made of these applications, and what kind of image processing you are doing with imagemagick and ghostscript.
If in any doubt, get a test vps set up of a similar specification that you would intend to deploy live, and load test your application using e.g apache ab while monitoring cpu and memory use.
If the cpu load is high for typical simulation then make sure any vps you use is a xen based one - this has better isolation between vps clients so is less likely to get the host to take action over sustained high resource use.