I often prefer the self service model, but other times I like talking to sales. Some of them are good (just happened yesterday) where they take time to understand your company and goals. He suggested their cheapest plan. You can often get deals. I know of a cloud hosting company that cuts outrageous deals if you talk to sales. Another gave a potential customer 80k in credit to leave AWS.

Most sales people aren't very good and there is a bad stigma that perpetuates