How much would copy promoting a new ebook cost for me?

Sorry, OP. Back to your question...

How much have you set aside to spend on your marketing? If you haven't made a marketing budget, do so now.

Plan ahead. Allocate your resources according to your needs, your skills and your bank balance.

For example, if you plan to market this ebook using, say, articles that you write yourself, then your marketing "cost" = "your time".

If you'll need to outsource your writing, how many articles do you plan to submit per week? Do you want to work with someone you can pick up the phone and call? Do you want someone competent enough to create articles that incorporate selling techniques and drive traffic directly, or someone who can write decent content that will get your articles republished elsewhere (one is sales; the other is PR).

Figure out whether you intend to aim for quantity or quality. In other words, if you want to move hundreds of copies of your ebook, quickly, you're going to want to make the price point an intrinsic part of your "irresistable offer". Or if your book has built-in red-hot appeal to a proven market of buyers, you can sell it just by letting them know where and how to get it.

In this case, you may not need long copy to sell it, and it may be the kind of project that is perfect for a beginning copywriter.

(Inexperienced copywriters combined with long copy is a train wreck waiting to happen. Yabbering on for 20 pages is useless unless you're saying all the right things. Inexperienced copywriters rarely know all the right things to say - yet. The result is irrelevance. Irrelevance is boring. Nothing kills your sale faster than being boring.)

OTOH, if you think you have a really high-quality product, and you want to sell it for reasonable coin, you'll need someone who can persuasively articulate the value you're bringing to the prospect. Those folks usually don't come cheap. However, don't despair...

Contact copywriters whose work you like, tell them about your project, tell them your budget (in an non-arrogant way!), and see if they can/will work with you. If it's obvious that you're not trying to nickle and dime them, you might be surprised at the result.

You see, a knowledgable copywriter will not quote you a figure until they know the size, scope, and intended market of the project. Because a knowledgable copywriter knows these things matter.

Frank Kern can send out an email saying, "Go buy this now" and make sales for a $2K product. Joe Whatsisname wouldn't make a dime using the same approach for a $2 product.

Like you, experienced copywriters like to know what they're in for - before they commit themselves.