I'd say it is worth it to breed your own mice veen if you only have 1 snake.

Think about it, you need a mouse every 5-7 days, so thats like 4-6 mice per month (about)

Go buy 2 males, and 6 females or 1 male and 3 females for a smaller breeding project. That will cost about $1.50-$3.00 per mouse.

Since you only have 1 snake I will assume that your going to start off with 1 male and 3 females.

Mice - $6-$12 (Total)
Bedding - $7 for 41 liters of aspen at petsmart (Lasts about 6 weeks)
Food - Mazuri rat/mouse diet $6 for a bag that will last you 5 weeks
Water - Barely anything.
Other things - excersize wheel, salt wheel, water dispenser, hide - $15 (make the hide out of a cheap dollar store plastic bowl)

Thats somewhere between $34-$45 for your startup cost. You can use cheap rubbermaid tubs (the big ones) to make a simple mouse/rat tub. Or use any spare 10 gallon tubs you have laying around. I made mine out of rubbermaid tubs (I made 4 of them for less than $30 total)

About every 6 weeks, you will need to buy more bedding and food, which will cost less than $15

After the startup costs, you will actually be saving money after X ammount of months. If you eventually have 2 snakes, youll be definately saving a lot....

BREED YOUR OWN MICE! It will eventually save money and it's a fun project.

Also, if you feed live mice, these people arnt even factoring in the cost of gas to drive to go get the mice.