As a marketer this bothers me. While I assume I am completely oversimplifying this statement, an ongoing bug bear of mine is business that treats marketing as an expense. Marketing is an investment. It should be treated and monitored as you would your investments. Adwords ads are not expensive, they have a positive or negative ROI/ROMI. It doesn't matter if a click cost $1 or $1,000, its about the following profit you get back from that click. You need to understand how you track + what your avg revenues and margins are. Adwords (and other channels) should never be expensive, they should be positive or negative returning assets.
> Has anyone done this before?
I've on both sides of contracting marketing. It makes sense to pay for specialization if you can earn a reasonable salary elsewhere.
> who do you outsource to?
Depends on what you need? Be careful going cheap. There is no industry accreditation and many people jump in selling promises they cant deliver. ALso yyou sound like you need someone that can advise you as much as 'do as I say' type contractor. Look for experience and someone that can show you specifically why they succeeded when they took of other marketing gigs. Don't go for the cheapest or biggest promise as an absolute.
> What does it cost ?Please share.
As above, you can do affiliate type deals where you only pay for success. Or you may pay $5 to $500/hr depending on what you look for. Try not to go in too light on spend. If you want to spend $500 on advertising anyone decent will cost more than that alone setting up a solid performing campaign. People often test with small amounts, hire some low cost person and then decide 'marketing doesn't work'. You need to do a shotgun type approach where you blast tests across a bunch of channels/approaches, see where the profit pattern is for you to chase. Also when you budget budget a decent spend in addition to a person. I see businesses hire a marketing person and then allocate not budget. Thats a waste of money unless they are literately after a blogger/web developer in one and that's all you want.