Amazon.co.uk offers The Bourne Collection on Blu-ray Disc
for $14.70 (£12). During checkout, it falls to $12.25
(£10). With $3.77
(£3.08) for shipping, that's the lowest total price we could find by $7, except for the mention below. (We did see it for $2 less in January.) This 4-disc set includes The Bourne Identity, The Bourne Supremacy, The Bourne Ultimatum, and The Bourne Legacy.
This Blu-ray set is region-free and the films themselves will play on US Blu-ray players, but note that the extras and special features may not. A close price: Megahitrecords via Amazon US
has it for $16.99 with free shipping for Prime members.