Maybe if you make one from start to finish with the intention of selling it, it wouldn't be as hard to part with it. The matter of its worth will always be difficult because only you will know what your time, effort and artistic value really are worth to you, but perhaps if you put it up for auction with a starting bid that reflects just the cost of material and a fixed value for your time, you may be pleasantly surprised what someone would be willing to pay - assuming the marketing is done effectively (ie, if it's a venue such as eBay, you have enough feedback points to assure potential bidders of your reliability, and the description is accurate and complete, the shipping reasonable, the pictures very clear. Having an auction end in the early evening of a weekend I have heard is also optimal.). Some quilt shows let quilters offer their works for sale. It might be worthwhile to check into that.
It's fairly certain that a person who is willing to pay a nice price for a quilt knows something about the value of it and will love having it, even though they don't know you personally. In fact, there's more assurance that it will be appreciated and cared for, perhaps, than if it is given to someone who may be "not that into quilts" as someone near to me was honest enough to say when I offered to make her one. It's possible that the experience of getting a good monetary value for your quilt will turn out to be quite rewarding, and if you start with just one you can say that you tried it and based your further decision about whether to sell on actual experience. From what others have said, it may not be a good idea to make a quilt to order because it seems like there are too many potential pitfalls, but the joy of making one exactly as you would like is still there, and just maybe others will be happy to demonstrate their appreciation for it by making a generous offer. Think of it as setting it free into the world - just one more way of sharing it with others.