Why this community will not facilitate a group purchase

Asking directly, because I could not find a straight answer: Why this community will not facilitate a group purchase

Currency and fees, set out so that the comparison can be checked.

Quoted amount, conversion rate applied, the spread on top of the mid-market rate, and any fixed fee: four numbers, and only the first is ever quoted. On my last two orders the difference between the quoted figure and the amount that left the account was not trivial.

Am I setting this comparison up correctly, or is there a component everyone else already accounts for?

Where a supplier issues a quote with an expiry, honouring it after the expiry is a courtesy rather than an entitlement, and several here have found it granted.

Scoping that to what I have actually seen rather than what I have read.

Confirming post #2 from a second method, which matters more than confirming it from a second person.

The practical questions in this subcategory are about recourse, records and timing, and none of them are chemistry. That is worth stating because the subcategory attracts chemistry answers.