is it safe to buy apple products from amazon.com

Normally Amazon products are fine. You should strongly consider buying direct from Apple, the reason is because when you buy from another reseller you are sacrificing many privileges such as if there is a problem you can return the machine within 14 days for ANY reason.

If money is your consideration then purchase an Apple refurbished machine, these have no downside! They are identical to new, come with the same warranty as new and eligible for AppleCare and can save hundreds of dollars! You can find them on Apple's online store, in the USA, click here.

I've bought a Mac mini via Amazon. It was (at the time) a recently discontinued model. It was complete, unopened, in its Apple packaging with all accessories and documentation (not, I should point out, that you get much in the way of documentation these days).

There are some current products a slightly lower prices - I'd expect them to be OK

I would double check the model number advertised by Amazon to make sure it is the current model. They may be selling older models at a discount.