Strong Buy
Grading Gyarados-EX (BREAKpoint) currently looks like a clear win. A 1981% Return on Grading comes from the spread between $79.39 raw and $3525.00 graded. Worth putting near the front of your next PSA submission.
Most grading maths asks you to guess your odds of a PSA 10 first. This works backwards from the prices instead and tells you what those odds would have to be.
The number is different on every card. It's how confident you'd need to be that this copy gems before grading pays for itself, so 20% means roughly a 1 in 5 shot and 50% means a coin flip.
Grade it if you rate your copy better than that, leave it raw if you don't.
It assumes a 9 is the worst you'll get. Centering and edge whitening send plenty of modern cards back at 8 or lower, and that's not priced in here, so treat this as the floor of the bar rather than the whole of it. Selling fees aren't counted either.
(cost - PSA 9) ÷ (PSA 10 - PSA 9)
Pays off even at PSA 9
A PSA 9 alone ($196.64) already covers your $169.39 cost (raw + grading + shipping), so you don't need the 10 to come out ahead.
Anything from a 9 upwards puts you ahead, and a 10 would net you $3355.61. The only real risk left is the card grading below a 9.
Among the 33 cards in BREAKpoint with PSA 10 sale data, Gyarados-EX ranks 5th for Return on Grading and 4th by PSA 10 price. Of the 9 Rare Ultra cards with PSA 10 sales, it is 4th for Return on Grading. The median PSA 10 in this set sells for $675.30. 26 of the 33 clear a 100% Return on Grading.