They (the online selling companies) heighten their prices...,

[Silverobama]

Every November 11th in China, online companies will sell their products cheaper than they used to be, and that day is called promotion day. I notice that actually the prices of many things are heightened, for example, a juicer is always sold at 300 yuan but at that promotion day it sells at 350, after that day it becomes 300 yuan again. So, basically, the products are sold at the original prices. I wrote:

They (the online selling companies) heighten their prices of the products on the promotion day and lower it again after the day is over; actually the prices of everything remain intact.

Please help me with a natural version of the italic sentence.

 

[tedmc]

I would use "mark up/raise" instead of heighten", and "are the same" instead of "remain intact".

 

[emsr2d2]

In China, Every on November 11th [every year] in China, online companies will sell their products cheaper than they used to be the rest of the year; and that day is called Promotion Day. However, I've noticed that actually the prices of many things are heightened actually higher. For example, a juicer is always normally sold at for 300 yuan but at that on Promotion Day it sells at it's sold for 350. After that, day it becomes reverts to 300 yuan. again. So, Basically, the products are sold at the original prices. I wrote:

They (the online selling companies) heighten raise/inflate their the prices of their products on the Promotion Day and lower it them again after the day is over the next day; actually the prices price of everything [actually] remains intact.

Please help me with a natural version of the italic sentence.

See above for my corrections. Neither underlined sentence makes sense. The items aren't sold at their "original price" on Promotion Day. They're sold at a different price (it happens to be higher). The price of everything doesn't remain intact - it fluctuates by going up on Promotion Day.