When searching online you have to guess how a website which might have what you are seeking has chosen to describe its wares. For example, when you go shopping do you:

1. Buy an item,

2. Purchase it,

3. Accept the valuation which they have placed on the item, or

4. Acquire it for a financial consideration?

OK, maybe the last one there is rather more formal than most websites are likely to use, but you get the point. English, because it is such a bastardised language, taking words via French and via German roots (and routes,) has a plethora of options for describing a single activity.

There is then the added issue that a 'sales' website might choose to not use the word for you to gain the object, but merely for them to make it available for sale. "We sell widgets" might as likely not include the words "purchase them here" or "buy them now", assuming the reader already looking at the website can recognise the options for your acquisition. The word 'Pay' could well be the nearest they come to suggesting a financial transaction is on offer.

Anyway, back to the searching …