There are a number of costs to importing:
1). The item price
2). International postage
These you will pay (but many Chinese/Hong Kong items are free post as the seller may be in a subsidised trading zone, and the international postal agreement treats them as a developing country)
3). There may be the option of “import insurance” or pre paid import fees to the seller
In theory this means the seller arranges payment of import duty / vat, but often means they just make false declarations and will refund your costs if it gets picked up
https://www.gov.uk/goods-sent-from-abroad/tax-and-duty
4) excise duty
Depending on the classification of the goods there may be excise duty. (Mainly booze & fags)
5) customs duty
The current threshold is £135.
If the goods assessed value is less than that, then you don’t pay customs duty
(But note that the valuation used may be the stated value on the declaration, or the goods are assessed at a value. These values used to exclude postage, but it is now taken into account)
6) Import VAT
If thresholds are exceeded then you get charged VAT at the current rate (20% for most goods)
This is where two thresholds apply - £15 for ‘goods’ or £39 for ‘gifts’
This is why many false declarations from China / Hong Kong state “gift” or “commercial sample”
If any of those apply and you haven’t a prearranged account then you get sent a bill
including carrier fees
7) carrier fees
These generally have been around £8 to £20, but do vary.
This is a fee raised by the importing carrier (not necessarily the carrier it was sent by as they may not have the international facilities)
It is for their staff to handle your item, the paperwork and for it to sit in their bonded warehouse etc
There is a way to avoid import costs - use UK retailers. Even if goods don’t appear to be available then contact some retailers, they may have them anyway, get it via their supplies or may import for you.
The benefit is you support UK retail, they will be importing somehow already and are likely to be able to do it more efficiently than you