5pcs 2 layer default settings 80x100mm boards ($4 vs EUR 124) is pretty much 30x.

I double checked because these were not the prices I had in mind.

After looking through the options, I think that's because the designs I did quotations for had 0.2mm holes. This is standard for Eurocircuits, but high precision for JLCPCB.

Note that to get the price you quoted, you'll get lead in your PCB, and vias that are not plated, but plugged with conductive epoxy. Changing that gets you to $14 for 5 boards, which is still way cheaper than Eurocircuits.

I'll keep that in mind for the next PCB I design: keep holes bigger than 0.3mm if possible.