How much do you need to pay for......

a really good converting sales letter?

I purchased a copywriter WSO for $97 for a sales letter but wasn't extremely happy with the sales letter.

I then changed the letter somewhat but my changed version didn't convert very well. So then I put up the original copywriters sales letter and sales just stopped completely.

Next a friend of mine wrote the sales letter for me and although I think it's good, it doesn't seem to be converting either.

The original copywriter has done me another sales letter that I haven't uploaded to try yet, but I have my doubts on its conversion.

There is another WSO out for sales letters at $147, but how do I know I'm not just going to spend more money for another sales letter that doesn't convert.

So I'm wondering how much do people like to pay for sales letters that they know they will be guaranteed to convert?

I do think I have a really good product here to offer people, but it isn't much good without a converting sales letter - I'm getting desperate but I really am a bit hesitant to spend more money without a guarantee I guess for conversion.

Any ideas???