Less expensive than injections. With injections you can easily spend ten times as much if you buy them from your doctor. If you buy them online you are still looking at about double the price.
No additional supplies. When you buy HCG drops, there are no additional supplies required to store, mix, or administer HCG itself. With injections and pharmaceutical drops, you have to pay extra for mixing supplies, storage supplies, and injection supplies.
No prescription. A single visit to the doctor for a consultation, and the resulting prescription, can easily cost anywhere from $50 to $200 or more. HCG drops don't require a doctor's approval.

But there are also less obvious ways that HCG drops -- and the HCG diet in general -- can help you save money:

No gym memberships. While taking HCG drops you do not need to exercise, and in fact you are discouraged from vigorous activity due to the lower calorie intake.
No fitness instructors or body building coaches. Again, no exercise means no additional expense in these areas.
No gadgets or equipment. You know those late-night infomercials that are always trying to sell you some new gadget or fancy equipment to help you lose weight? And then they throw in a dozen other "bonuses" needed for success. There's nothing like that with HCG drops. It's just the drops and instructions, that's it. Extra supplies can help but are optional.
Fewer groceries. While taking HCG drops you are only eating 500 calories per day. HCG uses your stored fat to power your body. It breaks down so much fat, some people can't even eat the usual 500 calories. You can save a huge amount on your grocery bill this way. And these savings continue after the diet as your smaller body requires fewer calories!
Less weight means fewer health problems. It's well known that obesity is associated with a number of other negative health conditions such as diabetes, high blood pressure, heart disease, and more. Losing weight is an investment in your long term health. You'll see money savings for a long time after you're done taking HCG drops.

So HCG drops can really save you a lot of money compared to other dieting methods--and compared to the alternative of staying obese.