You can build a $250 DIY lamp using four QB132 3.5K V1 ($109 for four) or V2 ($135 for four), a 1750a driver, and wiring/connectors. @imSICKkid just built a nice one for a square space. I have built one for a 2x4 rectangular space.
It would be more than enough light for a 60cmx60cm at ~1000ppfd. You can dim it in vegetative cycle to save energy.
Here’s a material list for all but the QBs themselves - goto the horticulture lighting group website for them.
There’s some pics of my assembly a bit down this post.