IANAL but, working at the other end of the (none bike related) chain my understanding is this:
Cost of return to point of purchase is the buyers’ to bear in [non DOA] warranty cases.
You return to the shop you bought it from at your cost# (even if that is just the kcal to walk there) [some online retailers will pay the cost but that’s entirely their perogative, don’t expect it off anyone else]
The shop returns to their supplier at their cost and so on up the chain.
Replacements (for faulty) are then shipped – in line with normal delivery terms – at suppliers cost* to their customer at original point of supply i.e. in store.
*if you want it sending to you this time instead of picking it up from store which you did last time I’d expect that cost to be passed on.
*I’d also expect you to pay for any special service you asked for – I.e. I want it FedEx to store tomorrow not on your regular delivery from supplier.
Of course many places may choose to do either of the above as good will but in no way would I think them obligated to do so.
<edit> # if it’s supplied as an installed item, say a washing machine, your home is point of supply as that’s where the final element of service took place.
If it’s supplied as a stand alone item i.e. an after market fork, the costs to return that part to stand alone status are also yours.
If it’s supplied as an integral part or pre installed component i.e. The fork on a new bike OR an aftermarket fork fitted by the items supplier where in its bought as a speed and installed item (not where you’ve paid your lbs to install a fork you bought from crc or you’ve payday the same lbs to supply out and install it as two distinct orders the cost of removal lies with the supplier of the complete item.(arguing the difference over an hour of mechanics time would seem petty but if it were say, a generator on a destroyer which needs a hole cut in the side and millions of pounds of work to replace it, becomes more pertinent),