Great question, and hopefully I can help as I’ve had experience managing delegate sales teams.
In essence, whether this would work for you depends on lots of variables. Some companies will let you hire sales people and pay them commission only, but this isn’t a great model and you won’t get great quality people representing your brand imo. Therefore you’d need to be able to afford a salary + commission, so it depends on how much each ticket sale is worth to you (and the sales person).
Then you’ve also got to consider how much data you have, and how good it is. A salesperson will often be required to do 100 dials a day, so do you have enough data to support that output? And do you have up to date contact details to provide them with? If not they’re going to waste a lot of time (and your money) trying to find the right details or just talking to the wrong person.
Then you’ve got to thoroughly brief them, manage them, review their pipeline etc.
If you’ve got a smallish target list of senior directors, you might be best carving out some time and calling them yourself.
That being said, the major conference companies employ telesales / delegate sales teams, so they do work (and in fact are necessary to sell enough high value tickets for some events)…but my guess is that for your needs, it might be overkill and a combination of email/social/seo + a few select calls from yourself might be most cost effective.