Over the weekend, my son who is really into Legos wanted a new set. So I shopped online to find best price on the particular set he wanted. Of all the retailers I searched, the cheapest one was Walmart.com.

My big surprise about Walmart prices

So we went to a nearby Walmart brick-and-mortar and found the Lego set he wanted on shelf. But the price on the shelf was about 35% higher than it was at Walmart.com!

I found an employee and showed them the online pricing from my smartphone. But I was told they don't match Walmart.com's prices. So I had to buy it on Walmart.com and do the free pickup option in the store to get the lower price.

My son and I stood there and watched as a different employee came a few minutes later, picked the item up off the shelf, and brought it back to the holding spot for pickup. Unfortunately, I didn't get the confirmation that it was available for pickup until the next day! So I had to go back the next day to pick it up!!

That's *not* good customer service.

But here's what you need to know. Pricing at Walmart.com has been completely separated from pricing at Walmart physical locations. Walmart.com has become an aggressive price competitor, while the Walmart prices at physical stores are not.

Sales at Walmart.com are up 30%, according to The Wall Street Journal, which is way outpacing growth at Amazon.com. It's gotten to the point that if Walmart.com were a standalone entity, it would be the world's second largest seller of goods on the Internet behind Amazon.

Now comes word that Walmart.com is also using dynamic demand pricing like the airlines, so the price of an item goes up and down like a yo-yo based on demand.

Amazon, meanwhile, is raising prices and counting on Prime members who historically don't comparison shop to continue that pattern. If you are a Prime customer, know you probably aren't getting the lowest price. If you're just into convenience, that's fine. But if you care about prices, you need to comparison shop. Amazon is now being underpriced in category after category.

It's your money; you make the choice.