Personally, I am against the "money only" request on wedding invitations. I have ruminated over the issue especially within the Samoan context and came up with the following.
GUEST vs. Donor
The main reason for inviting people to a wedding is for them to witness and help celebrate - the happy occasion - with the families and the newlyweds. Those who are invited are called guests - not customers, clients or donors. Therein lies the important difference and a particular for consideration.
Again, a guest (malo/malo faaaloalogia) is someone you invite to come and celebrate an occasion with you. You don't demand and/or impose things on a guest. Once you impose something on a guest, he/she becomes less of a guest and more of a donor or benefactor. Respect governs and underpins the host/guest etiquette and relationship. It involves the host honoring and respecting the guest's choice of what he/she brings. Incidentally, the quest is not obligated to bring anything but since there are rules of propriety and genteelness, a guest will always bring something. As a host, you don't tell or suggest to the guest to bring a specific gift - especially money. Simply, it's rude, offensive, disrespectful and egregious.
BIG WEDDING vs. small wedding
Generally speaking, Samoans like "BIG" weddings. In fact the so-called "Samoan wedding" is synonymous with a "BIG wedding". These are often held in big halls with average crowds of 300-500 people/guests, with copious foods and other forms of exchange including traditional wealth (fine mats, tapa cloths, etc.). Money also is often gifted by the host families, mainly to the VIPs in Samoan weddings.
The best estimate for the total average expenses for a typical "Samoan wedding" is around US$10,000.
That being said, I do have a problem with a typical "Samoan wedding" that sends out invitations with the "money only" request. It would be better off if the thousands of dollars intended for the wedding expenses be given to the bride and groom to start their family, and just have a small reception. But, ironically, Samoans also want big weddings - in some cases - to showcase family status and wealth and in such situations, invitations should not ask and/or stipulate "money only" gifts. If anything, they (hosts) should instead hand out money to the guests - at least for accepting the invitations. Please do not treat a BIG wedding as a business venture where you "spend money to make money" for the couple.
A small wedding, on the other hand, in the backyard or some other setting, would not and should not need a lot of invitations with stipulations anyway. Such weddings are only for families and close friends and acquaintances.
Now here's another aspect of a Samoan wedding that should negate the "money only" request. It's found in the traditional appreciation speech (faafetai) by the hosts. It speaks to the fact that guests already have their contribution just by showing up. Here's an applicable sample from a typical faafetai speech:
"...o ai le tagata ua e manatu ane ai? Faafetai atu i le talia faaaloalo o le faatalau'ula atu a aiga-na-lua ma le ulugalii fou. O lo tou faamalo'ulo'u, maliu mai ma tala mai o a'ao, ua maualuga ma matagofie ai le aso o Toleafoa ma Fuatino."
(...who are we that you have spared a thought of coming? Thank you for accepting the invitation by the families and the newlyweds. Your presence has only made this day more special and beautiful for Toleafoa and Fuatino.)
Now some people interpret this to be nothing more than rhetoric and platitude - if not part of the typical reserved modesty (faafitifitiga) common in these such speeches. I would beg to differ though. I personally believe that there's honest appreciation, sincerity and truth in such expressions albeit seemingly trite and cliched. What if you had sent out 500 invitations and only 30 or 10 people showed up? The fact that people accepted and came is something for which the hosts should be indeed grateful. And if you start placing demands and stipulations on the guests, then it seems that these people showed up of their own volition - and were not invited.
Again, please do not make stipulations and/or demands on the guests. E le'i alanoa le tala ane o a'ao o le ‘au vala'aulia. Na ala ona o ane ona o lau vala'au faaaloalo. Afai fo'i e te manatu i sauniuniga e iai taumafa ma nisi tulaga, ia o mea na sa saunia e tali ai malo (‘au valaaulia), e pei lava o tu ma agaifanua masani a Samoa. E le'i saunia ina ia faia ai ni fefaataua'iga - Leai! O ni mana'oga e foliga mai e faamalosi (demands) pe fai fa'a-tuutuuga (stipulations), e le talafeagai i tulaga i le va feagai o le malo (guest) ma le talimalo (host), ae maise le tu faaaloalo i ni malo.
Lastly, if the couple gets 20 toasters, 40 towel sets, 30 glassware sets, etc. - all the better. Keep them, distribute them or if possible return them for cash or store credit. Look on the bright side, toasters are getting more expensive by the year, so keep them as a lifetime supply. Likewise with other gifted items.
Ia manuia le ulugalii fou. Ia fua tele le niu, moli, kuava ma la'au uma o le faato'aga. Ia fua mai fo'i nisi la'au i tupe. Methinks that money will eventually grow on trees...LOL!!