Controversial opinion, but if you can’t afford a venue for a Friday, Saturday or Sunday, then you can’t afford that venue. When DH were in that boat, we realised we needed to cut our cloth accordingly and had a DIY wedding reception on a bank holiday Saturday. It was a lot of work, but our small budget shouldn’t have turned into our guests’ problem.
We booked the cheapest venue that would suit our needs for the wedding (had to accommodate 100 guests, and a ceilidh). Even so, we couldn't afford a weekend rate and therefore had to choose a weekday. We were both students (Masters and PhD) with almost no savings. Everything else we did for the wedding was completely geared towards our guests (we had 3 menus to cater for vegetarians, vegans, and meat-lovers, we supplied free booze to everyone, we helped everyone find and book accommodation, we paid for everyone's taxis).
I think it's unfair to just assume that a weekday wedding is because the couple are self-centred or are trying to live above their means. For us, it was necessary to get married when we did as we were moving to a country where it is illegal to cohabit without a marriage certificate.
Despite the ball-ache of having a weekday wedding, everyone who was near and dear to us managed to make it (with the exception of one of my SILs who had contracted a vomiting bug on the day of her flight - she still managed to Skype us during the wedding to say congratulations!). Everyone said they enjoyed our wedding, and that they appreciated the thought we put into it.
Wish that there was a little more empathy for couples who don't have copious amounts of funds, or much choice in dates rather than assuming that they're being selfish and self-centred.