Purchasing yarn for a specific project can get expensive, especially if the pattern calls for several different colors, or if it is a set of something, like a baby outfit that has a hat, sweater, booties, and blanket. How a pattern is written can make a difference in how much you spend and if you will have enough yarn or way too much left over, thereby costing you more than you would really need. Patterns that are offered by a yarn company have an objective in selling you their yarn - so if they can write a pattern in such a way that you will buy 2 balls of yarn instead of 1 - then they win, and you have alot of left-overs.
Recently I wanted to work on a crocheted baby sweater that was all one color and used worsted weight acrylic yarn.The directions said I needed 2 skeins of yarn, each 5 ounces, for the sweater, which is quite alot for such a small project. The project also had booties, a hat and a blanket, which called for an additonal 4 skeins of yarn. I already had a large 1 pound skein of similar yarn on hand, so decided to use that for the sweater.
The directions called for first using one ball of yarn to work the body of the sweater, bottom up, work up to underarm area and stop, leaving the yarn attached to the sweater body, then with a second ball of yarn, make first one sleeve, end it off, and make the second.Then the sleeves were attached to the body of the sweater, and the top completed.
Here is where I realized that if the pattern instructions had been written differently, there would not be a need for a second ball of yarn. If the sleeves had been worked first with the one ball of yarn, the ends cut and woven in, and the body of the sweater worked second with the same ball of yarn, there would not be a need for second ball of yarn to make just that sweater. By needing only that one ball of yarn for the sweater, the cost was less, and there was less waste. I'll admit here that leftover yarn isn't necessarily a bad thing, and can be worked into other projects, but if you are short on funds, spending needlessly takes the joy out of a project, or might cause you turn away from a project because of the cost of the yarn stated to complete the item.
My advice here is to read thru the pattern instructions first before purchasing the yarn, and see if you can identify ways to make the project in a different order so as not to need as much yarn. That will save you money in the end.
A note on working with multi-colors: This can be quite expensive when it comes to purchasing the called-for colors in a pattern, for something like a ski sweater, or multi-colored socks. You may only need to work one or two rows of a contrasting color, leaving you with most of a ball of yarn unused. Here again read thru the pattern and think if it would be possible to not use as many colors in the project, possibly making the project with only 2 or 3 contrasting colors instead of 5 or 6. That will help make a project less expensive.