I thought they were cheap. We reserved a 2 bedroom for spring break a couple years that were 7680 points that cost us about $700 in MFs.
It depends on where you go and how long ago you booked.
1) They have no 2 BR Grand Luxxe units available you can only book Studio or 1 BR units at Nuevo Vallarta (which is ironic since it's significantly larger than Riviera Maya)
2) There are NO Grand bliss units anywhere (it's either Grand Mayan or Grand Luxxe). Personally I find the Grand Mayan beds to be hard as a rock vs. Grand Bliss/Grand Luxxe. But everyone has a bed preference.
3) Current point levels for Grand Luxxe 1 BR at both locations is: 20,160 HGV points. If you can get a 2 BR in Riviera Maya it's 23,040 points. Everyone's got a different MF ratio (mine was about $0.18/point under the old scale, and now it's $0.13/point with the new 60% "more"). So let's see, 20,000 points at $0.13/point = $2,600 in cost if I book 1 BR Grand Luxxe via Hilton. I can rent a 2 BR for $2500 or so from an owner on redweek or, USED to be able to deposit my 2,400 point Vegas Unit with SFX (at $432 plus the booking/Guest cert) and get a free upgrade to 2 BR and pay the extra $300 upcharge and $150 exchange fee which would've put me somewhere around $1,132 if I could exchange via SFX.
4) Grand Mayan units at Riviera Maya/Nuevo are 5,440 and 7,680 now for 1 BR/2BR respectively (my cost around $700/$1,000) vs. $780/$780 direct with SFX (although would be cheaper to use a Bonus week for the 1 BR as it negates the $150 exchange fee). So very close for 1 BR Grand Mayan.
YMMV (some folks like Grand Mayan or acapulco or don't need a 2 BR).