While the average cost of advertising in the local paper (or magazine) can range between a few hundred dollars and a few thousand (or a thousand to tens of thousands in the national paper depending on placement), this doesn't take into account having an advertorial being written for you. 

An intermediate copywriter (3-5 years) will typically create an advertorial for you in the paper for $0.12 to $0.50 per word, while a more experienced copywriter will charge $0.50 to $1.00+ per word. 

Advertising agencies who have in-house copywriters (or freelance copywriters) may also choose to charge a flat-rate fee or by the hour. 

When I quote a client for work, I usually provide three options with quotes close in price to allow clients to choose the method they're most comfortable with.

For example, if a client came to me to write a 550 to 600-word advertorial that I quoted at 4 hours, I would charge (or quote) the following:

A $.80 per-word option that could range between: $440 to $480 depending on the number of words the advert comes out to. (with an upfront deposit of $220)

A $110 hourly option for the first 4 hours I quoted and then a reduced rate of $50 per hour once I pass the quoted time. (with an upfront deposit of $220.)

A flat-rate fee of $460 with half being paid upfront and the rest paid on completion. 

You would then add the copywriter's fee on top of the publication's fee. 

Advertising agencies may charge an additional publishing fee as well. 

I hope this answered your question and wasn't too confusing! :)