Amazon is a wild, seemingly random marketplace. Prices are largely jumping around all of the time for several reasons:
- Sellers compete for the buy box by dropping their price
- Sellers use software to automate a pricing strategy (such as Splitly)
- Sellers increase their prices to reduce number of sales if they are running low on stock
- Sellers manually drop or raise prices to compete against their competition
- Sellers issue temporary discounts to increase sales and gain traction
- Sellers' costs increase or decrease, leading to changing product prices
If you take a good look at Amazon, you'll see that pricing just isn't constant. Sellers are jumping their price around because the world just isn't in a stable condition. Customers on Amazon also know this too - many websites have jumping prices, not just Amazon.
If you aren't testing your prices then guess what - your competitors probably are - and they're probably more optimum than you.
If you're worried that customers might ask for a refund because the product is now a little bit cheaper, this cost to your business is negligible compared to the gains in revenue you will make by changing your price and finding the optimum price point.
The opposite is also true: if you increase your price, buyers might be forced to make a buying decision there and then because they are worried the price may go up further.
TL;DR: worrying about refunds is a negligible cost to finding the right price point. Finding the right price point is paramount to selling on Amazon and if that means a few refunds or returns, so be it.