Samsung's latest flagship phones are already turning heads, but the prices for the new devices are all over the place.

A new Galaxy S9 starts at $720, while the Galaxy S9 Plus starts at $840. But depending on the carrier you buy it on, you might pay a lot more.

T-Mobile matches Samsung's price, but for a limited time. AT&T's S9 costs $70 more at $790 and the S9 Plus costs $75 more at $915. Sprint offers both phones around the same price.

Verizon and Best Buy's prices are the highest with an S9 costing $800 and the S9 Plus costing $930 -- $90 more than buying direct from Samsung.

That said, Best Buy is offering $100 off when you preorder either phone, making it one of the "best" deals: $700 for an S9 and $830 for an S9 Plus. Best Buy is also letting customers combine that $100 discount with a trade-in discount of up to $350 -- $450 off -- when you preorder the phones on Friday, March 2.

The cheapest deal so far is from Xfinity Mobile. You can get an S9 for $270 -- that's after $450 in discounts. Read on for all the details and fine print.

Check out the chart below to compare prices.

Galaxy S9 and S9 Plus prices compared

	Galaxy S9 price	Galaxy S9 Plus price	Trade-in discount	Additional discounts
Samsung	$720	$840	Up to $350
T-Mobile	$720	$840	Up to $360
Xfinity Mobile	$720	$840	At least $200 or more	Get a $250 prepaid Visa card -- offer ends March 22.
US Cellular	$759	$920	Up to $350	Receive $250 in bill credits if you don't trade-in a phone.
AT&T	$790	$915	Up to $350	Gain $150 in bill credits for porting over to a new line.
Sprint	$792	$912	Up to $350	Get $150 Visa gift card with or without a trade-in
Best Buy	$800	$930	Up to $350	Save $100 off with carrier plan when preordered Friday, March 2. This can be combined with trade-in discount for up to $450 off.
Verizon	$800	$930	Up to $350	Get a $150 prepaid MasterCard for porting over to a new line.

Editors' note: As more deals are announced, we'll update this article.

Announcement

Samsung announced the Galaxy S9 and S9 Plus at Mobile World Congress on Sunday. It kept all the wonderful things about last year's S8 and S8 Plus -- like their design and size -- and improved on some of the less wonderful things, like the placement of the rear fingerprint reader. Our first look at the Galaxy S9 and S9 Plus is already online for you to read.

Preorders and launch

You will be able to preorder a Galaxy S9 or S9 Plus on Friday, March 2 at 12:01 a.m. EST from Samsung, carriers and third-party retailers. The phones go on sale two weeks later on March 16. For everything you need to know about preordering the S9, check out our story.

Trade-in: $350 off

Most, if not all, of the carriers and third-party retailers are offering up to $350 off the S9 and S9 Plus for trading in an old phone. Newer phones such as the Samsung Galaxy Note 8, Apple's iPhone X and the Galaxy S8 will fetch you $350 off, while older phones such as the iPhone SE, Note 4 and Galaxy S5 will earn you $100 off. For more details on the trade-in program check out our story.

You can buy an unlocked S9 for $720 or $30 a month for 24 months from Samsung's website or the Shop Samsung Android app. An unlocked S9 Plus is $840 or $35 a month for 24 months.

Living up to its name, Best Buy offers you $100 off either phone when you preorder them Friday, March 2 on an AT&T, Sprint or Verizon plan. That's on top of trade-in savings of up to $350 off. If you got the full $450 discount, an S9 would "cost" $350 and an S9 Plus would be $480.

If you miss the preorder Friday deal, you can save up to $100 off either phone when you preorder them starting Saturday, March 3.

You can also buy an unlocked S9 or S9 Plus from Best Buy on March 16 and still get the trade-in deal. Best Buy offers 24-month financing when using a My Best Buy Credit Card.

For a limited time, T-Mobile will sell the S9 for $720 or $30 a month for 24 months and the S9 Plus for $840 or $30 a month for 24 months after a $120 downpayment.

In the fine print, it doesn't state when exactly the "limited time" offer expires, but it does express that this discount price "may not be combined with some offers or discounts."

If you trade in an old phone, T-Mobile will give you 24 monthly bill credits totaling up to $360.

A Galaxy S9 will cost you $33.33 per month for 24 months ($800) at Verizon. The S9 Plus will be $39 per month for 24 months ($930).

You can get up to $350 off by trading in your old phone in the form of a bill credit.

If you're buying an S9 or S9 Plus and porting in a new line of service, Verizon will give you a $150 prepaid MasterCard.

You can also get discounts on Samsung tablets and Gear S3 smartwatches when you buy an S9 or S9 Plus on a two-year contract. Verizon Up customers with an active Samsung phone will receive an offer for $10 off select Samsung accessories.

AT&T offers a $150 bill credit when you bring a line from another carrier. This is in addition to the trade-in offer of up to $350 in bill credits (minimum of $200 trade-in credit on any phone with at least a $20 value).

What's interesting is the language around the trade-in's: Guaranteed minimum $350 when trading in a Samsung Galaxy S8 family or Note 8, iPhone 8, 8 Plus or iPhone X; LG V30; Google Pixel 2/XL Phone. So there could be a chance you get more than $350 for trading one of those phones in.

If you're an AT&T Next customer, you can buy an S9 for $26 for 30 months -- $790 total. The S9 Plus is $30 over 30 months -- that's $915. No word if the price is different for buying either phone outright.

You can lease an S9 from Sprint for just $13.55 a month or an S9 Plus for $18.55 a month on an 18-month Sprint Flex plan. That price includes a $150 Visa gift card and the full $350 trade-in -- which means you're trading in a Galaxy S8/S8 Plus or an iPhone X, 8/8 Plus.

Comcast aka Xfinity Mobile guarantees at least $200 for trade-ins. No word yet on what the highest trade-in for a phone is. To sweeten that deal they are also giving away a $250 prepaid Visa card when you purchase a Samsung phone with a new line of service. The gift card deal expires March 22, 2018.

This means you can pick up an S9 for $270 or an S9 Plus for $390 after trade-in and the promo gift card is factored in.

The Galaxy S9 from US Cellular is $759 or $25.30 a month on a 30 month plan. The S9 Plus is $920 or $30.65 a month on a 30 month plan.

You can get $250 in bill credits or you can get up to $350 in bill credits when you trade-in a phone.

You will be able to preorder the S9 and S9 Plus from Costco, but beyond that there's no specifics on prices or discounts.

You can get the S9 and S9 Plus on an AT&T, Sprint or Verizon carrier plan from Target. Like Costco, there's no word on price.

Galaxy S9 and S9 Plus​: Hands-on with Samsung's iPhone X fighters.

MWC 2018: All of CNET's coverage from the biggest phone show of the year.

First published Feb. 25, 10:34 a.m. PT.
Update, Feb. 26 at 11:53 a.m.: Adds Costco and Target.

Update, Feb. 26 at 2:19 p.m.: Adds monthly plan cost for US Cellular.

Update, Mar. 1 at 5:02 p.m.: Updates monthly plan cost for AT&T and Sprint.