One reason for being so cheap is that these glass downlights are on clearance now, so they are available only as stock lasts! The Garda Square / Garda Round glass ceiling downlights use a regular GU10 max 50W light bulb, and they are 115mm diameter (or 115mm x 155mm, if square). The Latina Glass Round / Square downlights are slightly smaller in size and only IP20 rated.
Latina 5505 Glass Round Recessed Ceiling Light
Latina 5506 Glass Square Recessed Ceiling Light
Garda 5520 Round Glass Bathroom Downlight
Garda 5521 Square Glass Bathroom Downlight
Read more about the Glass Downlights for Bathroom Ceiling via the recessed lights at Sparks, to have some more variety of fittings in the same style and shape.