Virgin Mobile USA, which is owned and run by Sprint, threw its hat in the iPhone prepaid ring Thursday. The company will begin selling the iPhone 4 and iPhone 4S to its customers starting June 29 with plans that cost as little as $30 per month. Virgin will offer the 8-GB iPhone 4 for $549 and the 16-GB iPhone 4S for $649.

Virgin's announcement followed the lead set by Cricket Wireless, which last week announced similar plans for the Apple iPhone. Cricket will sell the Apple iPhone 4 and iPhone 4S starting June 22. The devices will cost $399 and $499, respectively, and can be matched to a voice and data plan that costs only $55 per month. No contract is required, and you can cancel the service any time you want.

Both offers are fairly enticing, but will you really save any money compared to the iPhone prices and plans offered by the major wireless network operators in the U.S.? Let's take a look.

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For the basis of this comparison, let's assume we're purchasing the 16-GB iPhone 4S and going with the absolute cheapest service plan options available from any given carrier. Even though Cricket and Virgin don't require contracts, let's use the 24-month period to provide a perspective on costs. Also, let's forget about taxes and just go with the raw figures we have, as wireless taxes vary by state. Last, since iPhones can use iMessage, which sends text/picture messages over the network rather than via traditional SMS/MMS pipes, we'll avoid adding extra messaging plans. Purely looking at the lowest possible choices from the providers below.

Cricket:

Cricket's 16-GB iPhone 4S costs $499 and must be matched with a $55 monthly plan. Cricket's plan offers unlimited voice minutes, messaging, and data. Spending $55 per month for 24 months totals $1,320. Toss in $499 for the iPhone and your base cost is $1,819.

Virgin Mobile USA:

Virgin Mobile USA's 16-GB iPhone 4S costs $649 and must be matched with a minimum $30 monthly plan. This minimum plan includes 300 voice minutes, unlimited messaging, and 2.5 GB of 3G data (before throttling). This plan also reflects a $5 discount if customers sign up for automatic payments. Spending $30 per month for 24 months totals $720. Toss in $649 for the iPhone and your base is $1,369. That's $450 cheaper than Cricket's plan.

AT&T:

If you go with Apple's long-time iPhone partner AT&T, you'll spend $199 on the 16-GB iPhone 4S. The minimum voice plan allowed costs $39.99 for 450 minutes. You can skip a messaging plan if you don't mind paying per message, but you must include a $20 monthly 300-MB data plan. As long as you don't send a single text, picture, or video message, you're looking at $59.99 times 24 months for a total of $1,440. Add the $199 for the iPhone itself and you're at $1,639. Updated with correct data allotment.

Sprint:

Sprint makes things fairly easy. The 16-GB iPhone 4S costs $199. Sprint offers an unlimited everything (including messaging) plan for $69.99 per month. So spending $70 per month for 24 months and you're looking at damage of $1,680. Include the $199 device cost, and you're looking at $1,879 over two years.

Verizon Wireless:

If you choose to go with Big Red instead of Cricket or Virgin, the 16-GB iPhone 4S costs only $199, but it requires a two-year contract. The absolute cheapest options available include a 450-minute voice plan at $39.99 per month and $30 2-GB data plan. If you want messaging, too, you'll either have to choose to pay by the message or fork over $10 for 1,000 messages or $20 for unlimited messages. If we go with the pay-by-use model, the absolute least you can spend with Verizon per month is $69.99. Spending $70 per month for 24 months and you're looking at damage of $1,680. Include the $199 device cost, and you're looking at $1,879 over two years.

Bottom Line:

Looking at the above options, the Virgin Mobile USA plan is the least expensive over the course of two years compared to the others. Granted, the comparisons here aren't equal in that they don't include equivalent minutes, messaging, and data--but they are the lowest rates available from each carrier discussed.

If you don't mind being limited to 300 voice minutes and just 2.5 GB of data, Virgin's deal is the one to pick.

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