john, I live in Bucharest, so I can't really give you advice on hotels, cuz I never stayed in one. However, WHERE that apartment is located is critical in Bucharest. Allthough I don't know what you preffer (quiet, nature, nightlife, etc.) I will list some parts of Bucharest that would be nice, with some specifics as to what you can expect:
1. Piata (square in Romanian) Romana - center, nightlife, noisy
2. Piata Universitatii - center, nightlife, noisy
3. Piata Aviotorilor / Kiseleff street / Primaverii region / Piata Viscoriei - lots of parks, quiet, may be more expensive than the first 2
4. Dacia street, Dorobanti region - balanced and OK in every respect
Al all costs avoid:
1. Piata Unirii, Piata Alba Iulia, the Unirii region alltogether (new center) - No parks, no trees, it's noisy, expensive and ugly
2. Cotroceni region - too far from anything
50 EUR for an apartment for 3 persons sounds reasonable, especially if it is located in one of those areas that I mentioned. As for "luxury", it may be a bit down to luck. Write me the name of the website where you found the apatments, I'll have a look to, and I may be able to give you some advice, living here I have an "eye" for these things, I don't necessarily have to see it with my own eyes. Also, if you want, tell me what you would like to do in Bucharest, so I can direct you to some places.
Peace