Up until 29th December you can buy Starwood Preferred Guest points which can convert into Marriott Rewards at a 35% discount. You can buy these on the SPG website.
You need to buy a minimum of 5,000 points, and can buy up to a maximum of 30,000 points which will cost you $682.50 (£522).
30,000 Starwood points would also convert into 90,000 Marriott Rewards points. If you are working towards a Marriott Travel Package redemption, then buying the full 30,000 Starwood points may well make sense.
This Venice hotel is a Marriott category 8 property which means I can stay here for a week on the Marriott Reward Plus Hotel & Air Package for 290,000 Marriott rewards or 96,000 spg points (as you can transfer them over at a rate of 1SPG=3 Marriott) PLUS I get 55,000 Air Miles (in my case I collect Avios which I value at around £0.02 per point making 55,000 worth £1100 to me). With the Marriott Reward Plus Hotel & Air Package, 96,000 spg points will get me a stay (7 nights) worth 2597€ ($3017)+ 55,000 Avios worth £1100 ($1438) of Avios. This values my SPG points at $4,455/96,000 = $0.046.
Alternatively, if I book 5 nights (which is probably long enough at this property) I can book 4 nights and get the 5th free which costs 160,000 Marriott points (53,333 SPG) in mid-August. I could book this for cash and it would cost me 1,855€ (371€ per night). This values my SPG points at $1,855/160,000 = 0.0116€*3 or $0.01 and my SPG points at $0.04.
Interestingly, with the Marriott Reward Plus Hotel & Air Package, 360,000 Marriott Rewards = 120,000 SPG will get me a 7-night stay worth 2597€ ($3017)+ 120,000 Avios which I value at £2400 ($3138) of Avios. This values my SPG points at $4,455/120,000 = $0.036.
If I purchase 30,000 points for $682.50 these are therefore worth $1,392 to me. Points post within 24 hours. Of course, your valuation of points and miles may well be different from mine!
Disclosure: Most of our property, service & product reviews are sponsored by the proprietor or brand being appraised. All opinions remain our own & are in no way influenced by any sponsor.