Oh yes they're pricey. (I'm assuming you're making a LEGO one?) That's about the size we did at BrickFair one year, and that was like between 7-8 people. I know I've spent $20-30 on bricks to fill just one 32x32 baseplate. Good luck! (And remember plates stacked on bricks totally count and can save you a bit)

For parts like 1x1 bricks that are useful for mosaics, one of the most cost-effective methods of buying them in bulk would be pick-a-brick. Not the online one, but rather the ones in Lego stores (which let you fill a container for a flat rate rather than charging you per-piece). Or even better, since store selection can be spotty and might have a lack of certain colors at any given time, the ones at Legoland parks (which from my experience carry a wide selection of basic bricks in all the most common colors).

I'm not suggesting making a trip to Legoland just to buy bulk bricks, but if there's a trip in your future it'd definitely be worth your while to take note of what parts you need beforehand.

For parts like 1x1 bricks that are useful for mosaics, one of the most cost-effective methods of buying them in bulk would be pick-a-brick. Not the online one, but rather the ones in Lego stores (which let you fill a container for a flat rate rather than charging you per-piece). Or even better, since store selection can be spotty and might have a lack of certain colors at any given time, the ones at Legoland parks (which from my experience carry a wide selection of basic bricks in all the most common colors).

 

I'm not suggesting making a trip to Legoland just to buy bulk bricks, but if there's a trip in your future it'd definitely be worth your while to take note of what parts you need beforehand.

That's a good idea. I don't live anywhere near a LEGO store, but I think my roommate does. I might be able to send him on a fetch quest. Thanks for the tip.

(Though I'll still need to BrickLink a bunch of things, the mosaic includes a lot of old light/dark gray pieces.)

e: oh wait durr I'm going to BrickFair, that's decently close to a LEGO Store.

The problem is that they usually don't have a ton of useful bricks in the right color. Another useful brick is the 2x2 corner brick, which is more useful in creating "angles" than using 3 1x1 bricks. I've seen corner bricks in dark blueish gray, but if you're insisting on classic gray, then the secondary market is probably your best bet.

The problem is that they usually don't have a ton of useful bricks in the right color. Another useful brick is the 2x2 corner brick, which is more useful in creating "angles" than using 3 1x1 bricks. I've seen corner bricks in dark blueish gray, but if you're insisting on classic gray, then the secondary market is probably your best bet.

Yeah, I want to use all the shades of gray I can because the image is mostly monochrome and that helps define it better.